Devices, systems and methods for refueling air vehicles

ABSTRACT

A variety of refueling devices, systems and methods are disclosed for use in in-flight refueling. In one example one such device is towed by a tanker aircraft via a fuel hose at least during in-flight refueling, and has a boom member with a boom axis. The boom member enables fuel to be transferred from the fuel hose to a receiver aircraft along the boom axis during in-flight refueling. The device maintains a desired non-zero angular disposition between the boom axis and a forward direction at least when the refueling device is towed by the tanker aircraft in the forward direction via the fuel hose.

TECHNOLOGICAL FIELD

The presently disclosed subject matter relates to systems and methodsfor refueling air vehicles, especially aircraft, in particular forrefueling aircraft during flight.

BACKGROUND

Airborne refueling (also referred to interchangeably herein as airrefueling, in-flight refueling, air to air refueling (AAR), aerialrefueling, tanking, and the like) refers to the process of transferringfuel from a tanker aircraft to a receiver aircraft during flight.

Two types of airborne refueling systems are currently in use forrefueling airborne military aircraft:

-   -   the so-called “hose and drogue” system, used by the US Navy and        many non-US air forces;    -   the so-called “boom and receptacle” or “flying boom” system,        used by the US Air Force, and also used by Israel, Turkey and        the Netherlands.

In the hose and drogue system, the refueling aircraft is provided withone or more non-rigid refueling lines, at the end of each of which thereis a drogue which functions as a stabilizer and includes a receptacle,while the receiver aircraft is fitted with a probe that is configuredfor engaging with the receptacle. In use, the drogue is not activelycontrolled, but rather aligns itself freely in the airflow aft of thetanker. The pilot of the receiver aircraft controls the flight paththereof to ensure engaging contact between the probe and the receptacle.Thereafter, the receiver aircraft is refueled via the refueling line andprobe.

In the boom and receptacle system, the tanker includes a so-called“flying boom”, which is a rigid tube that telescopes outwardly and isgimbaled to the rear of the tanker aircraft, and is otherwise retractedinto the tanker fuselage when not in use. The boom carries a fuel lineand comprises a fuel transfer nozzle at the end thereof, and the boom isequipped with adjustable flight control surfaces. Once the tanker andreceiver aircraft are in close proximity and flying in formation, withthe receiver aircraft at a position behind the tanker within an airrefueling envelope (i.e., safe limits of travel for the boom withrespect to the receiver aircraft and within which contact between thereceiving aircraft and the boom is safe), a dedicated operator in thetanker controls the position of the boom via the control surfaces, andinserts the end of the boom including the nozzle into a receptacleprovided on an upper part of the receiving aircraft, ensuring propermating between the nozzle and receptacle, after which fuel transfer canbegin. During refueling, and while the boom is engaged with thereceptacle, the pilot of the receiver aircraft must continue to flywithin the air refueling envelope, and if the receiver aircraftapproaches these limits the operator in the tanker requires the receiveraircraft pilot to correct the position thereof, and if necessary theboom is disconnected to prevent accidents. All current tankers of thistype carry a single boom and can refuel a single receiver aircraft ofthis type at a time.

In addition, there are some tankers that comprise a flying boom systemand at least one hose and drogue system as well, and are commonly knownas Multi-Point Refueling Systems (MPRS). In some cases a hose and droguesystem is provided at the aircraft tail, and thus only this system orthe flying boom system may be used at any one time. In other cases, twounder-wing hose and drogue pods, known as Wing Air Refueling Pods(WARPs), can be provided, one under each wing, in addition to the flyingboom system.

U.S. Pat. No. 7,562,847 discloses an autonomous in-flight refueling hoseend unit including a first end configured to be coupled to a fuel hoseof a tanker aircraft. and a second end configured to be coupled toreceiver aircraft and adjustable control surfaces, and a flight controlcomputer autonomously controls the control surfaces to fly the refuelinghose end into contact with the receiver aircraft.

In GB 2,237,251 an in flight refueling apparatus mountable on a tankeraircraft has a probe receptor coupled with a fuel line and is arrangedto be deployed outboard of the aircraft, and can be provided on a drogueor a boom. In one mode, the apparatus is arranged to provide a parameterwhich is representative of the deviation of the path of the receptorfrom a predetermined initial path for actuating control means forchanging automatically the position of the receptor relative to theinitial path. In another mode, a parameter which is representative ofthe relative angular position of the receptor with respect to the probeof an approaching refueling aircraft for actuating control means forchanging automatically the relative angular position to achievealignment of receptor and probe.

Additional references considered to be relevant as background to thepresently disclosed subject matter are listed below: US 2007/108339, US2007/084968, US 2006/065785, US 2006/043241, US 2006/060710, US2006/060709, US 2005/224657, US 2004/102876, U.S. Pat. No. 7,097,139,U.S. Pat. No. 6,966,525, U.S. Pat. No. 6,994,294, U.S. Pat. No.6,644,594, U.S. Pat. No. 5,906,336, U.S. Pat. No. 5,785,276, U.S. Pat.No. 5,499,784, U.S. Pat. No. 5,326,052, U.S. Pat. No. 4,282,909, U.S.Pat. No. 4,126,162, U.S. Pat. No. 4,072,283, U.S. Pat. No. 3,948,626,U.S. Pat. No. 3,091,419, U.S. Pat. No. 3,059,895, U.S. Pat. No.2,954,190, U.S. Pat. No. 2,582,609, U.S. D 439,876, DE 100 13 751.

Acknowledgement of the above references herein is not to be inferred asmeaning that these are in any way relevant to the patentability of thepresently disclosed subject matter

GENERAL DESCRIPTION

In accordance with an aspect of the presently disclosed subject matter,there is provided a variety of refueling devices, systems and methodsfor use in in-flight refueling. In at least one example one such deviceis towed by a tanker aircraft via a fuel hose at least during in-flightrefueling, and has a boom member with a boom axis. The boom memberenables fuel to be transferred from the fuel hose to a receiver aircraftalong the boom axis during in-flight refueling. The device maintains adesired non-zero angular disposition between the boom axis and a forwarddirection at least when the refueling device is towed by the tankeraircraft in the forward direction via the fuel hose.

In accordance with an aspect of the presently disclosed subject matter,there is provided a method for controlling in-flight refueling of areceiver aircraft having a fuel receptacle, comprising automaticallysteering a refueling device to an engagement enabling position,including:

-   -   (i) repeatedly determining a spatial disposition of the        refueling device with respect to the receiver aircraft, the        refueling device being capable of engaging and refueling the        receiver aircraft via a boom member, when the device arrives to        the engagement enabling position at which the boom member is in        a predetermined spaced and spatial relationship with respect to        the fuel receptacle of the receiver aircraft;    -   (ii) repeatedly calculating steering commands based at least on        the repeatedly determined spatial dispositions and        characteristics of a spatial control system of the refueling        device;    -   (iii) sending the steering commands to the spatial control        system;    -   whereby at the engagement enabling position, the boom member of        the refueling device is capable of engaging with the fuel        receptacle to enable refueling of the receiver aircraft.

The method can optionally further comprise one or more of the features(c1) to (c15), in any desired combination or permutation:

(c1) providing an instruction to the refueling device, in response toits arriving at the engagement enabling position, causing the refuelingdevice to move the boom member in a predetermined trajectory forautomatically engaging with the fuel receptacle.

(c2) wherein the boom member has a boom axis and wherein at least afinal part of the predetermined trajectory is parallel to the boom axis.

(c3) determining an engagement area specification condition; repeatedlycalculating maneuvering instructions for the receiver aircraft based onthe spatial dispositions and an engagement area specification; andinvoking the automatic steering in response to meeting the engagementarea specification condition.

(c4) wherein the refueling device is connected to a tanker aircraft by afuel hose, and further comprising providing the maneuvering instructionsto at least one of a pilot of the receiver aircraft pilot or a pilot ofthe tanker aircraft.

(c5) wherein providing the maneuvering instructions comprises activatinga signaling system, optionally mounted on the refueling device or thetanker aircraft.

(c6) activating a force generating arrangement in the refueling devicefor generating force in the direction of the fuel receptacle of thereceiver aircraft in response to receiving an engagement command forenabling refueling.

(c7) wherein the determining a spatial disposition comprises acquiringan image of said receiver aircraft, comparing the image with a referenceimage depicting a desired spatial disposition of the refueling devicewith respect to a receiver aircraft, and determining, based on thecomparing, the spatial disposition of the refueling device with respectto the receiver aircraft.

(c8) wherein the spatial control system characteristics are related tooperation parameters of aero-dynamic control surfaces of the refuelingdevice.

(c9) wherein the aero-dynamic control surfaces are one or more vanes.

(c10) wherein the spatial control system characteristics are related tooperation parameters of reaction control thrusters associated with therefueling device and capable of steering the refueling device.

(c11) wherein the engagement area specification condition is a spatialdisposition within a pre-determined volume with respect to the refuelingdevice and wherein the pre-determined volume is optionally substantiallyin the shape of a cube or substantially in the shape of a sphere.

(c12) wherein the calculating steering commands comprises obtaining dataof an initial trail position of the refueling device and wherein thesteering commands are based also on the data of an initial trailposition.

(c13) wherein the data of an initial trail position includes at leastone of a pitch angle of the refueling device, a yaw angle of therefueling device, and a deployment length of a fuel hose connecting therefueling device to the tanker aircraft.

(c14) wherein the automatic steering and the automatic engaging areperformed autonomously by the refueling device.

(c15) wherein said refueling device is non-aircraft-fixed.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a method for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising:

-   -   (a) automatically steering a refueling device to an engagement        enabling position, including:        -   (i) repeatedly determining a spatial disposition of the            refueling device with respect to the receiver aircraft, the            refueling device being capable of engaging and refueling the            receiver aircraft via a boom member, when the device arrives            to the engagement enabling position at which the boom member            is in a predetermined spaced and spatial relationship with            respect to the fuel receptacle of the receiver aircraft;        -   (ii) repeatedly calculating steering commands based at least            on the repeatedly determined spatial dispositions and            characteristics of a spatial control system of the refueling            device;        -   (iii) sending the steering commands to the spatial control            system;    -   (b) providing an instruction to the refueling device, when it        arrives at the engagement enabling position, for causing the        refueling device to move the boom member along a predetermined        trajectory for automatically engaging with the fuel receptacle.

The method can optionally further comprise one or more of the features(c2) and/or (c4) to (c15) detailed hereinabove and/or one or more of thefeatures (d1) to (d2), in any desired combination or permutation:

(d1) invoking the automatic steering in response to a spatialdisposition between the refueling device and the receiver aircraftmeeting an engagement area specification condition.

(d2) repeatedly calculating maneuvering instructions for the receiveraircraft based on spatial dispositions and an engagement areaspecification, for establishing the spatial disposition between therefueling device and the receiver aircraft that meets the engagementarea specification condition.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a method for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising:

-   -   (a) repeatedly calculating maneuvering instructions for the        receiver aircraft based on spatial dispositions of the receiver        aircraft and an engagement area specification until an        engagement area specification condition is met;    -   (b) in response to meeting the engagement area specification        condition, automatically steering a refueling device to an        engagement enabling position, including:        -   (i) repeatedly determining a spatial disposition of the            refueling device with respect to the receiver aircraft, the            refueling device being capable of engaging and refueling the            receiver aircraft via a boom member, when the refueling            device arrives to the engagement enabling position at which            the boom member is in a predetermined spaced and spatial            relationship with respect to the fuel receptacle of the            receiver aircraft;        -   (ii) repeatedly calculating steering commands based at least            on the repeatedly determined spatial dispositions and            characteristics of a spatial control system of the refueling            device;        -   (iii) sending the steering commands to the spatial control            system;    -   (c) providing an instruction to the refueling device, in        response to its arriving at the engagement enabling position,        causing the refueling device to move the boom member in a        predetermined trajectory for automatically engaging with the        fuel receptacle.

The method can optionally further comprise one or more of the features(c2) and/or (c4) to (c15) detailed hereinabove, in any desiredcombination or permutation.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a system for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising asteering control module configured to automatically steer a refuelingdevice to an engagement enabling position, including:

-   -   (i) repeatedly determine a spatial disposition of the refueling        device with respect to the receiver aircraft, the refueling        device being capable of engaging and refueling the receiver        aircraft via a boom member, when the device arrives to the        engagement enabling position at which the boom member is in a        predetermined spaced and spatial relationship with respect to        the fuel receptacle of the receiver aircraft;    -   (ii) repeatedly calculate steering commands based at least on        the repeatedly determined spatial dispositions and        characteristics of a spatial control system of the refueling        device;    -   (iii) send the steering commands to the spatial control system        for automatically steering the refueling device to the        engagement enabling position;    -   whereby at the engagement enabling position, the boom member of        the refueling device is capable of engaging with the fuel        receptacle to enable refueling of the receiver aircraft.

The system can optionally further comprise one or more of the features(c2) and/or (c8) to (c11) and/or (c13) and/or (c15) detailed hereinaboveand/or one or more of the features (e1) to (e10), in any desiredcombination or permutation:

(e1) an engagement/disengagement module configured to provide aninstruction to the refueling device, in response to its arriving at theengagement enabling position, causing the refueling device to move theboom member in a predetermined trajectory to automatically engage withthe fuel receptacle.

(e2) a maneuvering instructions module configured to determine anengagement area specification condition, to repeatedly calculatemaneuvering instructions for the receiver aircraft based on the spatialdispositions and an engagement area specification, and to invoke thesteering control module to automatically steer the refueling device tothe engagement enabling position in response to meeting the engagementarea specification condition.

(e3) wherein the refueling device is connected to a tanker aircraft by afuel hose, and wherein the maneuvering instructions module is furtherconfigured to provide the maneuvering instructions to at least one of apilot of the receiver aircraft pilot or a pilot of the tanker aircraft.

(e4) wherein the maneuvering instructions module is configured toactivate a signaling system in order to provide the maneuveringinstructions, the signaling system is optionally mounted on therefueling device or the tanker aircraft.

(e5) wherein the engagement/disengagement module is further configuredto activate a force generating arrangement in the refueling device forgenerating force in the direction of the fuel receptacle of the receiveraircraft in response to receiving an engagement command for enablingrefueling.

(e6) wherein the steering control module is configured to perform thefollowing steps in order to determine a spatial disposition: acquire animage of the receiver aircraft; compare the image with a reference imagedepicting a desired spatial disposition of the refueling device withrespect to a receiver aircraft; determine, based on the comparing, thespatial disposition of the refueling device with respect to the receiveraircraft.

(e7) wherein the steering control module is further configured to obtaindata of an initial trail position of the refueling device and whereinthe calculate steering commands is based also on the obtained data of aninitial trail position.

(e8) wherein at least the steering control module and theengagement/disengagement module are fitted within the refueling devicefor enabling autonomously controlling in-flight refueling of thereceiver aircraft by the refueling device.

(e9) wherein at least the steering control module and theengagement/disengagement module are fitted within the receiver aircraft.

(e10) wherein at least the steering control module and theengagement/disengagement module are fitted within the tanker aircraft.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a system for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising asteering control module configured to automatically steer a refuelingdevice to an engagement enabling position, including:

-   -   (i) repeatedly determine a spatial disposition of the refueling        device with respect to the receiver aircraft, the refueling        device being capable of engaging and refueling the receiver        aircraft via a boom member, when the device arrives to the        engagement enabling position at which the boom member is in a        predetermined spaced and spatial relationship with respect to        the fuel receptacle of the receiver aircraft;    -   (ii) repeatedly calculate steering commands based at least on        the repeatedly determined spatial dispositions and        characteristics of a spatial control system of the refueling        device;    -   (iii) send the steering commands to the spatial control system        for automatically steering the refueling device to the        engagement enabling position;    -   the system further comprises an engagement/disengagement module        configured to provide an instruction to the refueling device,        when it arrives at the engagement enabling position, for causing        the refueling device to move the boom member along a        predetermined trajectory to automatically engage with the fuel        receptacle.

The system can optionally further comprise one or more of the features(c2) and/or (c7) to (c11) and/or (c13) and/or (c15) and/or (e3) to (e5)and/or (e7) to (e10) detailed hereinabove and/or one or more of thefeatures (f1) to (f2), in any desired combination or permutation:

(f1) a maneuvering instructions module configured to invoke the steeringcontrol module to automatically steer the refueling device to theengagement enabling position in response to meeting an engagement areaspecification condition.

(f2) wherein the maneuvering instructions module is further configuredto repeatedly calculate maneuvering instructions for the receiveraircraft based on spatial dispositions and an engagement areaspecification, for establishing the spatial disposition between therefueling device and the receiver aircraft that meets the engagementarea specification condition.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a system for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising amaneuvering instructions module configured to repeatedly calculatemaneuvering instructions for the receiver aircraft based on spatialdispositions of the receiver aircraft and an engagement areaspecification until an engagement area specification condition is met,and in response to meeting the engagement area specification condition,activate a steering control module; the steering control module isconfigured to automatically steer a refueling device to an engagementenabling position, including:

-   -   (i) repeatedly determine a spatial disposition of the refueling        device with respect to the receiver aircraft, the refueling        device being capable of engaging and refueling the receiver        aircraft via a boom member, when the device arrives to the        engagement enabling position at which the boom member is in a        predetermined spaced and spatial relationship with respect to        the fuel receptacle of the receiver aircraft;    -   (ii) repeatedly calculate steering commands based at least on        the repeatedly determined spatial dispositions and        characteristics of a spatial control system of the refueling        device;    -   (iii) send the steering commands to the spatial control system        for automatically steering the refueling device to the        engagement enabling position;    -   the system further comprises an engagement/disengagement module        configured to provide an instruction to the refueling device, in        response to its arriving at the engagement enabling position,        causing the refueling device to move the boom member in a        predetermined trajectory to automatically engage with the fuel        receptacle.

The system can optionally further comprise one or more of the features(c2) and/or (c7) to (c11) and/or (c13) and/or (c15) and/or (e3) to (e5)and/or (e7) to (e10) detailed hereinabove, in any desired combination orpermutation.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a method for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising:

-   -   automatically maneuvering a refueling device to an engagement        enabling position, including:    -   (i) repeatedly determining a spatial disposition of the        refueling device with respect to the receiver aircraft, the        refueling device being capable of engaging and refueling the        receiver aircraft via a boom member, when the device arrives to        the engagement enabling position at which the boom member is in        a predetermined spaced and spatial relationship with    -   (ii) repeatedly calculating maneuvering commands based at least        on the repeatedly determined spatial dispositions and        characteristics of a spatial control system of the refueling        device;    -   (iii) sending the maneuvering commands to the spatial control        system;    -   whereby at the engagement enabling position, the boom member of        the refueling device is capable of engaging with the fuel        receptacle to enable refueling of the receiver aircraft.

The method can optionally further comprise one or more of the features(c1) and/or (c2) and/or (c5) and/or (c7) and/or (c9) and/or (c11)detailed hereinabove and/or one or more of the features (g1) to (g12),in any desired combination or permutation:

(g1) wherein the refueling device is non-aircraft-fixed and wherein themaneuvering commands are steering commands for steering the refuelingdevice in six degrees of freedom.

(g2) wherein the refueling device is aircraft fixed and wherein themaneuvering commands are alignment commands for aligning the refuelingdevice in three degrees of freedom.

(g3) determining an engagement area specification condition; repeatedlycalculating maneuvering instructions for the receiver aircraft based onthe spatial dispositions and an engagement area specification; andinvoking the automatically maneuvering in response to meeting theengagement area specification condition.

(g4) providing the maneuvering instructions to at least one of a pilotof the receiver aircraft or a pilot of a tanker aircraft.

(g5) wherein the refueling device is non-aircraft-fixed and wherein themethod further comprising activating a force generating arrangement inthe refueling device for generating force in the direction of the fuelreceptacle of the receiver aircraft in response to receiving anengagement command for enabling refueling.

(g6) wherein the determining a spatial disposition comprises: acquiringan image of the receiver aircraft, the image comprising depth data andelectromagnetic data; comparing the depth data and the electromagneticdata with look-up tables comprising reference depth data and referenceelectromagnetic data relating to reference spatial dispositions withrespect to the receiver aircraft; determining, based on the comparing,the spatial disposition of the refueling device with respect to thereceiver aircraft.

(g7) wherein the image is acquired by a Light Detection And Ranging(LIDAR) unit.

(g8) wherein the refueling device is non-aircraft-fixed and wherein thespatial control system characteristics are related to operationparameters of aero-dynamic control surfaces of the refueling device.

(g9) wherein the refueling device is non-aircraft-fixed and wherein thespatial control system characteristics are related to operationparameters of reaction control thrusters associated with the refuelingdevice and capable of maneuvering the refueling device.

(g10) wherein the calculating maneuvering commands comprises obtainingdata of an initial trail position of the refueling device and whereinthe maneuvering commands are based also on the data of the initial trailposition.

(g11) wherein the refueling device is non-aircraft-fixed and wherein thedata of the initial trail position includes at least one of a pitchangle of the refueling device, a yaw angle of the refueling device, anda deployment length of a fuel hose.

(g12) wherein the automatically maneuvering and the automaticallyengaging are performed autonomously by the refueling device.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a method for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising:

-   -   (a) automatically maneuvering a refueling device to an        engagement enabling position, including:        -   (i) repeatedly determining a spatial disposition of the            refueling device with respect to the receiver aircraft, the            refueling device being capable of engaging and refueling the            receiver aircraft via a boom member, when the device arrives            to the engagement enabling position at which the boom member            is in a predetermined spaced and spatial relationship with            respect to the fuel receptacle of the receiver aircraft;        -   (ii) repeatedly calculating maneuvering commands based at            least on the repeatedly determined spatial dispositions and            characteristics of a spatial control system of the refueling            device;        -   (iii) sending the maneuvering commands to the spatial            control system;    -   (b) providing an instruction to the refueling device, when it        arrives at the engagement enabling position, for causing the        refueling device to move the boom member along a predetermined        trajectory for automatically engaging with the fuel receptacle.

The method can optionally further comprise one or more of the features(c2) and/or (c5) and/or (c7) and/or (c9) and/or (c11) and/or (g1) to(g12) detailed hereinabove, in any desired combination or permutation.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a method for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising:

-   -   (a) repeatedly calculating maneuvering instructions for the        receiver aircraft based on spatial dispositions of the receiver        aircraft and an engagement area specification until an        engagement area specification condition is met;    -   (b) in response to meeting the engagement area specification        condition, automatically maneuvering a refueling device to an        engagement enabling position, including:        -   (i) repeatedly determining a spatial disposition of the            refueling device with respect to the receiver aircraft, the            refueling device being capable of engaging and refueling the            receiver aircraft via a boom member, when the refueling            device arrives to the engagement enabling position at which            the boom member is in a predetermined spaced and spatial            relationship with respect to the fuel receptacle of the            receiver aircraft;        -   (ii) repeatedly calculating maneuvering commands based at            least on the repeatedly determined spatial dispositions and            characteristics of a spatial control system of the refueling            device;        -   (iii) sending the maneuvering commands to the spatial            control system;    -   (c) providing an instruction to the refueling device, in        response to its arriving at the engagement enabling position,        causing the refueling device to move the boom member in a        predetermined trajectory for automatically engaging with the        fuel receptacle.

The method can optionally further comprise one or more of the features(c2) and/or (c5) and/or (c7) and/or (c9) and/or (c11) and/or (g1) and/or(g2) and/or (g4) to (g12) detailed hereinabove, in any desiredcombination or permutation.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a system for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising:

-   -   a steering control module configured to automatically maneuver a        refueling device to an engagement enabling position, including:    -   (i) repeatedly determine a spatial disposition of the refueling        device with respect to the receiver aircraft, the refueling        device being capable of engaging and refueling the receiver        aircraft via a boom member, when the device arrives to the        engagement enabling position at which the boom member is in a        predetermined spaced and spatial relationship with respect to        the fuel receptacle of the receiver aircraft;    -   (ii) repeatedly calculate maneuvering commands based at least on        the repeatedly determined spatial dispositions and        characteristics of a spatial control system of the refueling        device;    -   (iii) send the maneuvering commands to the spatial control        system for automatically maneuvering the refueling device to the        engagement enabling position;    -   whereby at the engagement enabling position, the boom member of        the refueling device is capable of engaging with the fuel        receptacle to enable refueling of the receiver aircraft.

The system can optionally further comprise one or more of the features(c2) and/or (c9) and/or (c11) and/or (e4) and/or (e6) and/or (e8) to(e10) and/or (g1) to (g2) and/or (g7) and/or (g9) and/or (g11) detailedhereinabove and/or one or more of the features (h1) to (h7), in anydesired combination or permutation:

(h1) an engagement/disengagement module configured to provide aninstruction to the refueling device, in response to its arriving at theengagement enabling position, causing the refueling device to move theboom member in a predetermined trajectory to automatically engage withthe fuel receptacle.

(h2) wherein the boom member has a boom axis and wherein at least afinal part of the predetermined trajectory is parallel to the boom axis.

(h3) a maneuvering instructions module configured to determine anengagement area specification condition, to repeatedly calculatemaneuvering instructions for the receiver aircraft based on the spatialdispositions and an engagement area specification, and to invoke thesteering control module to automatically maneuver the refueling deviceto the engagement enabling position in response to meeting theengagement area specification condition.

(h4) wherein the maneuvering instructions module is further configuredto provide the maneuvering instructions to at least one of a pilot ofthe receiver aircraft or a pilot of a tanker aircraft.

(h5) wherein the refueling device is non-aircraft-fixed and wherein theengagement/disengagement module is further configured to activate aforce generating arrangement in the refueling device for generatingforce in the direction of the fuel receptacle of the receiver aircraftin response to receiving an engagement command for enabling refueling.

(h6) wherein the steering control module is configured to perform thefollowing steps in order to determine a spatial disposition: acquiringan image of the receiver aircraft, the image comprising depth data andelectromagnetic data; comparing the depth data and the electromagneticdata with look-up tables comprising reference depth data and referenceelectromagnetic data relating to reference spatial dispositions withrespect to the receiver aircraft; determining, based on the comparing,the spatial disposition of the refueling device with respect to thereceiver aircraft.

(h7) wherein the steering control module is further configured to obtaindata of an initial trail position of the refueling device and whereinthe calculate maneuvering commands is based also on the obtained data ofthe initial trail position.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a system for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising:

-   -   a steering control module configured to automatically maneuver a        refueling device to an engagement enabling position, including:    -   (i) repeatedly determine a spatial disposition of the refueling        device with respect to the receiver aircraft, the refueling        device being capable of engaging and refueling the receiver        aircraft via a boom member, when the device arrives to the        engagement enabling position at which the boom member is in a        predetermined spaced and spatial relationship with respect to        the fuel receptacle of the receiver aircraft;    -   (ii) repeatedly calculate maneuvering commands based at least on        the repeatedly determined spatial dispositions and        characteristics of a spatial control system of the refueling        device;    -   (iii) send the maneuvering commands to the spatial control        system for automatically maneuvering the refueling device to the        engagement enabling position;    -   the system further comprises an engagement/disengagement module        configured to provide an instruction to the refueling device,        when it arrives at the engagement enabling position, for causing        the refueling device to move the boom member along a        predetermined trajectory to automatically engage with the fuel        receptacle.

The system can optionally further comprise one or more of the features(c2) and/or (c9) and/or (c11) and/or (e4) and/or (e6) and/or (e8) to(e10) and/or (g1) to (g2) and/or (g7) and/or (g9) and/or (g11) and/or(h2) to (h7) detailed hereinabove, in any desired combination orpermutation.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a system for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising:

-   -   a maneuvering instructions module configured to repeatedly        calculate maneuvering instructions for the receiver aircraft        based on spatial dispositions of the receiver aircraft and an        engagement area specification until an engagement area        specification condition is met, and in response to meeting the        engagement area specification condition, activate a steering        control module;    -   the steering control module is configured to automatically        maneuver a refueling device to an engagement enabling position,        including:    -   (i) repeatedly determine a spatial disposition of the refueling        device with respect to the receiver aircraft, the refueling        device being capable of engaging and refueling the receiver        aircraft via a boom member, when the device arrives to the        engagement enabling position at which the boom member is in a        predetermined spaced and spatial relationship with respect to        the fuel receptacle of the receiver aircraft;    -   (ii) repeatedly calculate maneuvering commands based at least on        the repeatedly determined spatial dispositions and        characteristics of a spatial control system of the refueling        device;    -   (iii) send the maneuvering commands to the spatial control        system for automatically maneuvering the refueling device to the        engagement enabling position;    -   the system further comprises an engagement/disengagement module        configured to provide an instruction to the refueling device, in        response to its arriving at the engagement enabling position,        causing the refueling device to move the boom member in a        predetermined trajectory to automatically engage with the fuel        receptacle.

The system can optionally further comprise one or more of the features(c2) and/or (c9) and/or (c11) and/or (e4) and/or (e6) and/or (e8) to(e10) and/or (g1) to (g2) and/or (g7) and/or (g9) and/or (g11) and/or(h2) and/or (h4) to (h7) detailed hereinabove, in any desiredcombination or permutation.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a non-aircraft-fixed refueling device foruse in in-flight refueling operation between a tanker aircraft and areceiver aircraft, comprising:

-   -   a selectively steerable body configured for being towed by the        tanker aircraft via a fuel hose at least during in-flight        refueling, and comprising a boom member having a boom axis and        configured to enable fuel to be transferred from the fuel hose        to the receiver aircraft along the boom axis during the        in-flight refueling operation;

a controller configured for selectively maneuvering the body to anengagement enabling position spaced with respect to the receiveraircraft and for aligning the boom axis in an engagement enablingorientation at the spaced position, and for subsequently moving the boommember along the boom axis towards the receiver aircraft for enablingfuel communication therebetween.

In accordance with an aspect of the presently disclosed subject matter,there is provided a method for controlling in-flight refueling of areceiver aircraft having a fuel receptacle, comprising automaticallyaligning a refueling device at an engagement enabling position,including:

-   -   (i) repeatedly determining a spatial disposition of the        refueling device with respect to the receiver aircraft, the        refueling device being capable of engaging and refueling the        receiver aircraft via a boom member, when the device arrives to        the engagement enabling position at which the boom member is in        a predetermined spaced and spatial relationship with respect to        the fuel receptacle of the receiver aircraft;    -   (ii) repeatedly calculating alignment commands based at least on        the repeatedly determined spatial dispositions and        characteristics of a spatial control system of the refueling        device;    -   (iii) sending the alignment commands to the spatial control        system;    -   whereby at the engagement enabling position, the boom member of        the refueling device is capable of engaging with the fuel        receptacle to enable refueling of the receiver aircraft.

The method can optionally further comprise one or more of the features(c1) to (c3) and/or (c5) and/or (c7) and/or (c11) detailed hereinaboveand/or one or more of the features (i1) to (i6), in any desiredcombination or permutation:

(i1) wherein the maneuvering commands are alignment commands foraligning said refueling device in three degrees of freedom.

(i2) providing the maneuvering instructions to at least one of a pilotof the receiver aircraft pilot or a pilot of the tanker aircraft.

(i3) determining an engagement area specification condition; repeatedlycalculating maneuvering instructions for said receiver aircraft based onsaid spatial dispositions and an engagement area specification; andinvoking said automatically aligning in response to meeting saidengagement area specification condition.

(i4) wherein the calculating alignment commands comprises obtaining dataof an initial trail position of the refueling device and wherein thealignment commands are based also on the data of an initial trailposition.

(i5) wherein the automatic aligning and the automatic engaging areperformed autonomously by the refueling device.

(i6) wherein said refueling device is aircraft fixed.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a method for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising:

-   -   (a) automatically aligning a refueling device at an engagement        enabling position, including:    -   (i) repeatedly determining a spatial disposition of the        refueling device with respect to the receiver aircraft, the        refueling device being capable of engaging and refueling the        receiver aircraft via a boom member, when the device arrives to        the engagement enabling position at which the boom member is in        a predetermined spaced and spatial relationship with respect to        the fuel receptacle of the receiver aircraft;    -   (ii) repeatedly calculating alignment commands based at least on        the repeatedly determined spatial dispositions and        characteristics of a spatial control system of the refueling        device;    -   (iii) sending the alignment commands to the spatial control        system;    -   (b) providing an instruction to the refueling device, when it        arrives at the engagement enabling position, for causing the        refueling device to move the boom member along a predetermined        trajectory for automatically engaging with the fuel receptacle.

The method can optionally further comprise one or more of the features(c2) and/or (c5) and/or (c7) and/or (c11) and/or (i1) to (i6) detailedhereinabove and/or feature (l1), in any desired combination orpermutation:

(l1) invoking the automatic aligning in response to a spatialdisposition between the refueling device and the receiver aircraftmeeting an engagement area specification condition.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a method for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising:

-   -   (a) repeatedly calculating maneuvering instructions for the        receiver aircraft based on spatial dispositions of the receiver        aircraft and an engagement area specification until an        engagement area specification condition is met;    -   (b) in response to meeting the engagement area specification        condition, automatically aligning a refueling device at an        engagement enabling position, including:    -   (i) repeatedly determining a spatial disposition of the        refueling device with respect to the receiver aircraft, the        refueling device being capable of engaging and refueling the        receiver aircraft via a boom member, when the refueling device        arrives to the engagement enabling position at which the boom        member is in a predetermined spaced and spatial relationship        with respect to the fuel receptacle of the receiver aircraft;    -   (ii) repeatedly calculating alignment commands based at least on        the repeatedly determined spatial dispositions and        characteristics of a spatial control system of the refueling        device;    -   (iii) sending the alignment commands to the spatial control        system;    -   (c) providing an instruction to the refueling device, in        response to its arriving at the engagement enabling position,        causing the refueling device to move the boom member in a        predetermined trajectory for automatically engaging with the        fuel receptacle.

The method can optionally further comprise one or more of the features(c2) and/or (c5) and/or (c7) and/or (c11) and/or (i1) to (i2) and/or(i4) to (i6) detailed hereinabove, in any desired combination orpermutation.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a system for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising asteering control module configured to automatically align a refuelingdevice at an engagement enabling position, including:

-   -   (iv) repeatedly determine a spatial disposition of the refueling        device with respect to the receiver aircraft, the refueling        device being capable of engaging and refueling the receiver        aircraft via a boom member, when the device arrives to the        engagement enabling position at which the boom member is in a        predetermined spaced and spatial relationship with respect to        the fuel receptacle of the receiver aircraft;    -   (v) repeatedly calculate alignment commands based at least on        the repeatedly determined spatial dispositions and        characteristics of a spatial control system of the refueling        device;    -   (vi) send the alignment commands to the spatial control system        for automatically steering the refueling device to the        engagement enabling position;    -   whereby at the engagement enabling position, the boom member of        the refueling device is capable of engaging with the fuel        receptacle to enable refueling of the receiver aircraft.

The system can optionally further comprise one or more of the features(c2) and/or (c11) and/or (i1) to (i2) and/or (i4) to (i6) detailedhereinabove and/or feature (o1), in any desired combination orpermutation:

(o1) a maneuvering instructions module configured to determine anengagement area specification condition, to repeatedly calculatemaneuvering instructions for the receiver aircraft based on the spatialdispositions and an engagement area specification, and to invoke thesteering control module to automatically align the refueling device atthe engagement enabling position in response to meeting the engagementarea specification condition.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a system for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising asteering control module configured to automatically align a refuelingdevice at an engagement enabling position, including:

-   -   (iv) repeatedly determine a spatial disposition of the refueling        device with respect to the receiver aircraft, the refueling        device being capable of engaging and refueling the receiver        aircraft via a boom member, when the device arrives to the        engagement enabling position at which the boom member is in a        predetermined spaced and spatial relationship with respect to        the fuel receptacle of the receiver aircraft;    -   (v) repeatedly calculate alignment commands based at least on        the repeatedly determined spatial dispositions and        characteristics of a spatial control system of the refueling        device;    -   (vi) send the alignment commands to the spatial control system        for automatically steering the refueling device to the        engagement enabling position;    -   the system further comprises an engagement/disengagement module        configured to provide an instruction to the refueling device,        when it arrives at the engagement enabling position, for causing        the refueling device to move the boom member along a        predetermined trajectory to automatically engage with the fuel        receptacle.

The system can optionally further comprise one or more of the features(c2) and/or (c7) and/or (c11) and/or (e4) to (e5) and/or (e8) to (e10)and/or (f2) and/or (i1) to (i2) and/or (i4) to (i6) detailed hereinaboveand/or one or more of the features (p1) to (p2), in any desiredcombination or permutation:

(p1) wherein the steering control module is further configured to obtaindata of an initial trail position of the refueling device and whereinthe calculate alignment commands is based also on the obtained data ofan initial trail position.

(p2) a maneuvering instructions module configured to invoke the steeringcontrol module to automatically align the refueling device to theengagement enabling position in response to meeting an engagement areaspecification condition.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a system for controlling in-flightrefueling of a receiver aircraft having a fuel receptacle, comprising amaneuvering instructions module configured to repeatedly calculatemaneuvering instructions for the receiver aircraft based on spatialdispositions of the receiver aircraft and an engagement areaspecification until an engagement area specification condition is met,and in response to meeting the engagement area specification condition,activate a steering control module; the steering control module isconfigured to automatically align a refueling device at an engagementenabling position, including:

-   -   (iv) repeatedly determine a spatial disposition of the refueling        device with respect to the receiver aircraft, the refueling        device being capable of engaging and refueling the receiver        aircraft via a boom member, when the device arrives to the        engagement enabling position at which the boom member is in a        predetermined spaced and spatial relationship with respect to        the fuel receptacle of the receiver aircraft;    -   (v) repeatedly calculate alignment commands based at least on        the repeatedly determined spatial dispositions and        characteristics of a spatial control system of the refueling        device;    -   (vi) send the alignment commands to the spatial control system        for automatically steering the refueling device to the        engagement enabling position;    -   the system further comprises an engagement/disengagement module        configured to provide an instruction to the refueling device, in        response to its arriving at the engagement enabling position,        causing the refueling device to move the boom member in a        predetermined trajectory to automatically engage with the fuel        receptacle.

The system can optionally further comprise one or more of the features(c2) and/or (c7) and/or (c11) and/or (e4) to (e5) and/or (e8) to (e10)and/or (i1) to (i2) and/or (i4) to (i6) and/or (p1) detailedhereinabove, in any desired combination or permutation.

In accordance with an aspect of the presently disclosed subject matter,there is yet further provided a refueling device for use in in-flightrefueling operation between a tanker aircraft and a receiver aircraft,comprising a selectively steerable body configured for being towed by atanker aircraft via a fuel hose at least during in-flight refueling, andcomprising a boom member having a boom axis and configured to enablefuel to be transferred from the fuel hose to a receiver aircraft alongthe boom axis during the in-flight refueling operation; a controllerconfigured for selectively steering the body to an engagement enablingposition spaced with respect to the receiver aircraft and for aligningthe boom axis in an engagement enabling orientation at the spacedposition, and for subsequently moving the boom member along the boomaxis towards the receiver aircraft for enabling fuel communicationtherebetween.

According to at least one aspect of the presently disclosed subjectmatter, there is provided a refueling device for use in in-flightrefueling operation between a tanker aircraft and a receiver aircraft,comprising:

-   -   a selectively steerable body configured for being towed by a        tanker aircraft via a fuel hose at least during in-flight        refueling, and comprising a boom member having a boom axis and        configured to enable fuel to be transferred from said fuel hose        to a receiver aircraft along said boom axis during said        in-flight refueling operation;    -   a controller configured for selectively steering the body to an        engagement enabling position spaced with respect to the receiver        aircraft and for aligning said boom axis in an engagement        enabling orientation at said spaced position, and for        subsequently moving the boom member along said boom axis towards        the receiver aircraft for enabling fuel communication        therebetween.

For example, moving the boom member along said boom axis towards thereceiver aircraft for enabling fuel communication therebetween can beachieved by any one of the following, for example:

-   -   by moving the body towards the fuel receptacle of the receiver        aircraft along the direction of the boom axis,    -   by telescopically extending the boom member towards the towards        the fuel receptacle of the receiver aircraft along said boom        axis while the body is maintained at the engagement enabling        position,    -   partially by moving the body towards the fuel receptacle of the        receiver aircraft along the direction of the boom axis, and        partially by telescopically extending the boom member towards        the towards the fuel receptacle of the receiver aircraft along        said boom axis while the body is maintained at the engagement        enabling position.

The refueling device according to this aspect of the presently disclosedsubject matter can optionally comprise a spatial control systemconfigured for selectively ensuring maintaining a desired non-zeroangular disposition between said boom axis and said forward direction atleast when said refueling device is towed by the tanker aircraft in saidforward direction via said fuel hose.

Additionally or alternatively to the above features, the refuelingdevice according to this aspect of the presently disclosed subjectmatter can optionally comprise one or more of features (A) to (S) below,additionally or alternatively including one or more of features (j1) to(j6) below, additionally or alternatively including one or more offeatures (k1) to (k15) below, additionally or alternatively includingone or more of features M1 and or M2 and/or (m1) to (m4) below,additionally or alternatively including one or more of features (n1) to(n4) below, additionally or alternatively including one or more offeatures (q1) to (q6) below, mutatis mutandis, in any desiredcombination or permutation.

Additionally or alternatively to the above features, the refuelingdevice according to this aspect of the presently disclosed subjectmatter can optionally comprise a force generating arrangement configuredfor selectively generating a force along said boom axis in a directiongenerally away from said fuel hose, i.e., towards the fuel delivery endof the boom member. Additionally or alternatively to the above features,the refueling device according to this aspect of the presently disclosedsubject matter can optionally comprise one or more of features (AA) to(LL) below, mutatis mutandis, in any desired combination or permutation.

Additionally or alternatively to the above features, the body accordingto this aspect of the presently disclosed subject matter can optionallycomprise a fuel delivery lumen configured for fluid communication withsaid fuel hose at least during the in-flight refueling operation, saidlumen being configured to enable fuel to be transferred from the fuelhose to a receiver aircraft during said in-flight refueling operation,and the fuel delivery device comprises a coupling having a hoseinterface configured for connecting said lumen to the fuel hose, saidcoupling configured for allowing relative rotation between the hose andsaid body in at least one degree of freedom while maintaining said fuelcommunication. Additionally or alternatively to the above features, therefueling device according to this aspect of the presently disclosedsubject matter can optionally comprise one or more of features (AAA) to(LLL) below, mutatis mutandis, in any desired combination orpermutation.

According to at least one aspect of the presently disclosed subjectmatter, there is provided a refueling device for use in in-flightrefueling operation, comprising:

-   -   a body having a longitudinal axis and configured for being towed        by a tanker aircraft via a fuel hose at least during in-flight        refueling operation, and comprising a boom member having a boom        axis and configured to enable fuel to be transferred from said        fuel hose to a receiver aircraft along said axis during said        in-flight refueling operation;    -   said boom member being pivotable with respect to said body,        between a retracted position and a deployed position, wherein in        said retracted position said boom axis is at a smaller angular        disposition with respect to said longitudinal axis than in said        deployed position    -   spatial control system including two sets of longitudinally        spaced control surfaces configured for enabling selectively        steering said refueling device while concurrently selectively        maintaining a desired non-zero angular disposition between said        boom axis and said longitudinal axis at least when said        refueling device is towed by the tanker aircraft in said forward        direction via said fuel hose.

The refueling device according to this aspect of the presently disclosedsubject matter can optionally comprise a spatial control systemconfigured for selectively ensuring maintaining a desired non-zeroangular disposition between said boom axis and said forward direction atleast when said refueling device is towed by the tanker aircraft in saidforward direction via said fuel hose.

Additionally or alternatively to the above features, the refuelingdevice according to this aspect of the presently disclosed subjectmatter can optionally comprise one or more of features (A) to (S) below,additionally or alternatively including one or more of features (j1) to(j6) below, additionally or alternatively including one or more offeatures (k1) to (k15) below, additionally or alternatively includingone or more of features M1 and or M2 and/or (m1) to (m4) below,additionally or alternatively including one or more of features (n1) to(n4) below, additionally or alternatively including one or more offeatures (q1) to (q6) below, mutatis mutandis, in any desiredcombination or permutation.

Additionally or alternatively to the above features, the refuelingdevice according to this aspect of the presently disclosed subjectmatter can optionally comprise a force generating arrangement configuredfor selectively generating a force along said boom axis in a directiongenerally away from said fuel hose, i.e., towards the fuel delivery endof the boom member. Additionally or alternatively to the above features,the refueling device according to this aspect of the presently disclosedsubject matter can optionally comprise one or more of features (AA) to(LL) below, mutatis mutandis, in any desired combination or permutation.

Additionally or alternatively to the above features, the body accordingto this aspect of the presently disclosed subject matter can optionallycomprise a fuel delivery lumen configured for fluid communication withsaid fuel hose at least during the in-flight refueling operation, saidlumen being configured to enable fuel to be transferred from the fuelhose to a receiver aircraft during said in-flight refueling operation,and the fuel delivery device comprises a coupling having a hoseinterface configured for connecting said lumen to the fuel hose, saidcoupling configured for allowing relative rotation between the hose andsaid body in at least one degree of freedom while maintaining said fuelcommunication. Additionally or alternatively to the above features, therefueling device according to this aspect of the presently disclosedsubject matter can optionally comprise one or more of features (AAA) to(LLL) below, mutatis mutandis, in any desired combination orpermutation.

According to at least one aspect of the presently disclosed subjectmatter, the refueling device comprises:

-   -   a) a body configured for being towed by a tanker aircraft via a        fuel hose at least during in-flight refueling operation, and        comprising a boom member having a boom axis and configured to        enable fuel to be transferred from said fuel hose to a receiver        aircraft along said axis during said in-flight refueling        operation;    -   (b) spatial control system configured for selectively ensuring        maintaining a desired non-zero angular disposition between said        boom axis and a forward direction at least when said refueling        device is towed by the tanker aircraft in said forward direction        via said fuel hose.

The above refueling device can optionally comprise one or more of thefollowing features, in any desired combination or permutation:

-   -   A. A controller configured for selectively steering the body to        an engagement enabling position spaced with respect to the        receiver aircraft and for aligning said boom axis in an        engagement enabling orientation at said spaced position, and for        subsequently moving the boom member along said boom axis towards        the receiver aircraft for enabling fuel communication        therebetween.    -   B. The boom member comprises a nozzle at a terminus thereof in        fluid communication with a fuel delivery lumen comprised in said        body, said nozzle being configured for reversible engagement        with a fuel receptacle of a receiver aircraft.    -   C. The fuel hose is substantially non-rigid and/or said body is        selectively steerable.    -   D. The desired non-zero angular disposition is selectively        controllable and/or said angular disposition is defined on a        vertical plane.    -   E. The spatial control system configured for at least        maintaining a selectively controllable non-zero angular        disposition between said boom axis and a datum direction        (different from said boom axis); the datum direction can be a        forward direction of the body, i.e., direction of motion of the        body when towed via the hose; the said angular disposition can        be or comprise an angle of attack of said boom axis with respect        to said forward direction.    -   F. The said angular disposition is such as to ensure that the        boom axis is at a predetermined design angle with respect to the        receiver aircraft, in particular with respect to a longitudinal        axis of the receiver aircraft; the design angle is such as to        ensure proper alignment and engagement between the nozzle and        the fuel receptacle; for example, the design angle may be        between about 25° and about 35°, for example about 30°.    -   G. The said angular disposition is defined about a pitch axis of        said refueling device. Additionally or alternatively, said        angular disposition is defined about at least one of a yaw axis        and a roll axis of said refueling device. Additionally or        alternatively, the said angular disposition is in a range        between about 5° and about 85°; preferably between about 10° and        about 80°; more preferably between about 15° and about 70°; more        preferably between about 20° and about 60°; more preferably        between about 25° and about 50°; more preferably between about        20° and about 40°; more preferably between about 25° and about        40°; more preferably between about 28° and about 32°; or said        angular disposition is about 30°.    -   H. Wherein said refueling device is configured for maintaining        said desired non-zero angular disposition between said boom axis        and said forward direction at least prior to engagement of said        nozzle with a fuel receptacle of a receiver aircraft that flying        in formation aft of the tanker aircraft.    -   I. Wherein said spatial control system is further configured for        selectively providing control moments in at least one of pitch,        yaw and roll wherein to enable the refueling device to be flown        while towed by the tanker aircraft in said forward direction via        said fuel hose.    -   J. Wherein said device can optionally comprise one or more of        the following features, in any desired combination or        permutation:    -   (j1) wherein said body is elongate having a longitudinal axis        generally aligned with said boom axis.    -   (j2) wherein said body comprises a longitudinal axis, and said        boom member is pivotably mounted with respect to said body, and        pivotable between a retracted position and a deployed position,        wherein in said retracted position said boom axis is at a        smaller angular disposition with respect to said longitudinal        axis than in said deployed position.    -   (j3) wherein in said retracted position said boom axis is at an        angular disposition with respect to said longitudinal axis of        between 0° and 15°, and wherein in said deployed position, said        angular disposition is greater than 15°.    -   (j4) wherein in said deployed position said boom axis is at an        angular disposition with respect to said longitudinal axis        between 20° to 40°.    -   (j5) wherein said boom member is in said deployed position        during said in-flight refueling operation.    -   (j6) wherein said body comprises a longitudinal axis, and said        boom member is mounted with respect to said body (for example        fixedly mounted, or non-pivotably mounted, or mounted for        relative translation therebetween), such as to maintain a        generally parallel spatial disposition between said boom axis        and said longitudinal axis at least during said in-flight        refueling operation.    -   K. Wherein said spatial control system comprises selectively        controllable aerodynamic control system. The selectively        controllable aerodynamic control system can optionally comprise        one or more of the following features, in any desired        combination or permutation:        -   (k1) wherein said selectively controllable aerodynamic            control system comprises a forward set of aerodynamic            control surfaces mounted to said body, and an aft set of            aerodynamic control surfaces mounted to said body in            longitudinally aft spaced relationship with respect to said            forward set of aerodynamic control surfaces.        -   (k2) a center of gravity of said body is disposed in            longitudinally intermediate said forward set of aerodynamic            control surfaces and said aft set of aerodynamic control            surfaces.        -   (k3) wherein said aft set of aerodynamic control surfaces            comprises at least two said control surfaces mounted to said            body in Vee configuration; or wherein said aft set of            aerodynamic control surfaces comprises a high H-tail            configuration, comprising two vertical stabilizers, one each            on either side of a horizontal stabilizer—the H-tail            configuration can be mounted to the upper side of the body,            and optionally: each vertical stabilizer comprises a            controllably pivotable rudder, and/or the horizontal            stabilizer comprises one, two or more pivotable elevators,            which optionally are controllably actuated by an actuator            system for example controlled by a controller.        -   (k4) wherein said aft set of aerodynamic control surfaces            further comprises at least one said control surfaces mounted            to said body in vertical configuration.        -   (k5) wherein said forward set of aerodynamic control            surfaces comprises at least two said control surfaces            mounted to said body in Vee configuration.        -   (k6) wherein said forward set of aerodynamic control            surfaces comprises at least four said control surfaces            mounted to said body in cruciform configuration, for example            cruciform “X” configuration or cruciform “+” configuration.        -   (k7) wherein at least one said control surface is pivotably            mounted to said body via a respective boss laterally            projecting from an outer surface of said body.        -   (k8) wherein each said boss houses an actuator configured            for actuating the respective control surface.        -   (k9) wherein each said boss comprises an aerofoil shaped            cross-sectional shape having a respective chord.        -   (k10) wherein each said chord is angularly displaced from            said boom axis such as to become generally aligned with said            forward direction when said boom axis is at said non-zero            angular disposition with respect to said forward direction.        -   (k11) wherein said forward set of aerodynamic control            surfaces comprises a canard configuration, and said aft set            of aerodynamic control surfaces comprises one or more wing            elements.        -   (k12) wherein said aft set of aerodynamic control surfaces            comprises an H-tail configuration, comprising two vertical            stabilizers, one each on either side of a horizontal            stabilizer; and/or wherein said forward set of aerodynamic            control surfaces comprises at least four said control            surfaces mounted to said body in cruciform configuration.        -   (k13) wherein said spatial control system is configured for            enabling the refueling device to be steered in one, or two,            or three degrees of freedom in translation, and in one, or            two, or three degrees of freedom in rotation, independently            of the tanker aircraft or of the refueling aircraft.        -   (k14) wherein said spatial control system is configured for            providing at least one of:            -   one or more of: sideslip, up/down translation,                forward-aft translation, relative to the tanker aircraft                and/or to the refueling aircraft, independently of                rotational moments in roll pitch and/or yaw;            -   rotational moments in one or more of roll pitch and/or                yaw, relative to the tanker aircraft and/or to the                refueling aircraft, independently of sideslip, up/down                translation, forward-aft translation.        -   (k15) wherein said spatial control system is configured for            providing an angle of attack for the body with respect to            the forward direction, between −10° and +10°.    -   L. Wherein said spatial control system comprises a thrust vector        system.    -   M. A force generating arrangement including one or more of:        -   M1—a force generating arrangement configured for selectively            generating a force along said boom axis in an aft direction,            i.e., a direction towards said nozzle. The force generating            arrangement can optionally comprise one or more of the            following features, in any desired combination or            permutation:            -   (m1) wherein said force generating arrangement comprises                a selectively deployable and/or actuable drag inducing                arrangement.            -   (m2) wherein said force generating arrangement comprises                a selectively deployable and/or actuable air brake                arrangement.            -   (m3) wherein said air brake arrangement comprises a                plurality of airbrakes laterally mounted to at least one                of said body and said boom member.            -   (m4) wherein said force generating arrangement is                configured for selectively generating said force along                said boom axis in a direction towards said nozzle                responsive to said nozzle being in predetermined                proximity to the fuel receptacle of the receiver                aircraft whereby to force said nozzle into engagement                with the fuel receptacle.        -   M2—an aerodynamic stabilizer arrangement, different from the            spatial control system, for example wherein said aerodynamic            stabilizer arrangement is in the form of a drogue structure            having a stowed configuration, in which drogue structure            generates a minimum drag, and a deployed configuration in            drogue structure generates greater drag than in the inactive            configuration.    -   N. Said body comprises a fuel delivery lumen configured for        fluid communication with said fuel hose and said boom member at        least during the in-flight refueling operation, and said body        comprises a coupling having a hose interface configured for        connecting said lumen to the fuel hose, said coupling configured        for allowing relative rotation between the hose and said body in        at least one degree of freedom while maintaining said fuel        communication. The coupling can optionally comprise one or more        of the following features, in any desired combination or        permutation:        -   (n1) wherein said coupling configured for allowing relative            rotation between the hose and said body in at least two            degrees of freedom.        -   (n2) wherein said coupling configured for allowing relative            rotation between the hose and said body in three degrees of            freedom.        -   (n3) wherein at least one said rotational degree of freedom            has the respective axis of rotation generally orthogonal to            a plane defining said non-zero angular disposition between            said boom axis and said forward direction.        -   (n4) wherein said coupling comprises a universal coupling.    -   O. Wherein said boom member is selectively reversibly        telescopically deployable along said boom axis with respect to        said body or wherein said boom member is not reversibly        telescopically deployable along said boom axis with respect to        said body.    -   P. Wherein said boom member is pivotably mounted to said body.    -   Q. A data acquisition system configured for providing spatial        data relating to a relative spatial disposition between a fuel        delivery nozzle of the refueling device and a fuel receptacle of        the receiver aircraft, to enable selectively controlling the        refueling device to provide automatic and/or autonomous and/or        manual engagement of the fuel delivery nozzle to the fuel        receptacle of the receiver aircraft. In at least one example,        the system comprises an imaging system for providing said data        including at least image data corresponding to a field of regard        with respect to the refueling device. The data acquisition        system can be in the form of an imaging system, and can        optionally comprise one or more of the following features, in        any desired combination or permutation:        -   (q1) wherein said imaging system is configured for providing            at least one of 2D images, stereoscopic images, and 3D            images of a volume defined by said field of regard.        -   (q2) wherein said imaging system is configured for providing            said image data in real time.        -   (q3) wherein said imaging system comprises or is operatively            connected to a computing system configured for identifying a            fuel receptacle of a receiver aircraft within said field of            regard from said image data, and for determining a spatial            disposition of said nozzle with respect to the fuel            receptacle.        -   (q4) wherein said imaging system comprises a first set of            electromagnetic energy modules configured for illuminating            said field of regard with electromagnetic energy (for            example laser energy), and a second set of electromagnetic            energy modules configured for receiving electromagnetic            energy from said illuminated field of regard.        -   (q5) wherein said imaging system comprises a first set of            electromagnetic energy modules configured for transmitting            electromagnetic energy in a direction generally along said            boom axis and generally opposed to said forward direction,            and a second set of electromagnetic energy modules            configured for receiving electromagnetic energy from a            direction generally along said boom axis and generally along            said forward direction.        -   (q6) wherein said imaging system comprises at least one            flash ladar unit and/or at least one LIDAR unit.    -   R. The controller can comprise, for example, a computer system,        operatively connected to said spatial data acquisition system        and/or to said spatial control system, and/or optionally        configured as an automatic or autonomous system for enabling        refueling device to be steered to an engagement enabling        position to provide engagement of the nozzle with the fuel        receptacle of the receiver aircraft, and thereafter enable        refueling of the receiver aircraft.    -   S. A suitable communication system to transmit image data and to        receive control commands/signals. For example, the        communications system can be operatively connected to the        controller for controlling operation of the refueling device.

According to at least one aspect of the presently disclosed subjectmatter, the refueling device comprises:

-   -   a body configured for connection to a tanker aircraft via a fuel        hose at least during in-flight refueling operation thereof while        said body is in towed configuration with respect to the tanker        aircraft via said fuel hose, and further comprising a        substantially rigid boom member having a boom axis and        configured to enable fuel to be transferred from the tanker        aircraft to a receiver aircraft during said in-flight refueling        operation;    -   spatial control system configured for selectively maintaining a        desired non-zero angular disposition between said boom axis and        a datum direction.

The refueling device according to this aspect of the presently disclosedsubject matter can optionally comprise one or more of the followingfeatures, in any desired combination or permutation:

-   -   Wherein said datum direction is parallel to a longitudinal axis        of the receiver aircraft.    -   The desired non-zero angular disposition is selectively        controllable.    -   The datum direction is different, i.e. non-parallel, from said        boom axis.    -   The datum direction can be parallel to a forward direction of        the body, i.e., direction of motion of the body when towed via        the hose.    -   The spatial control system is also configured for selectively        ensuring maintaining a desired non-zero angular disposition        between said boom axis and said forward direction at least when        said refueling device is towed by the tanker aircraft in said        forward direction via said fuel hose.    -   The boom member comprises a nozzle at a terminus thereof in        fluid communication with a fuel delivery lumen comprised in said        body, said nozzle being configured for reversible engagement        with a fuel receptacle of a receiver aircraft.

Additionally or alternatively to the above features, the refuelingdevice according to this aspect of the presently disclosed subjectmatter can optionally comprise one or more of features (A) to (S),additionally or alternatively including one or more of features (j1) to(j6), additionally or alternatively including one or more of features(k1) to (k15), additionally or alternatively including one or more offeatures M1 and/or m2 and/or (m1) to (m4), additionally or alternativelyincluding one or more of features (n1) to (n4), additionally oralternatively including one or more of features (q1) to (q6), mutatismutandis, in any desired combination or permutation.

According to at least one other aspect of the presently disclosedsubject matter, the refueling device comprises:

-   -   (aa) a body configured for being towed by a tanker aircraft via        a fuel hose at least during in-flight refueling operation, and        comprising a boom member having a boom axis and configured to        enable fuel to be transferred from said fuel hose to a receiver        aircraft along said axis during said in-flight refueling        operation;    -   (bb) a force generating arrangement configured for selectively        generating a force along said boom axis in a direction generally        away from said fuel hose.

A fuel delivery nozzle is comprised at a terminus of the boom member andis in fluid communication with a fuel delivery lumen comprised in saidbody, the lumen configured for fluid communication with said fuel hoseand said fuel member at least during in flight refueling operation, saidnozzle being configured for reversible engagement with a fuel receptacleof a receiver aircraft.

The refueling device according to this aspect of the presently disclosedsubject matter can optionally comprise one or more of the followingfeatures, in any desired combination or permutation:

-   -   (AA) Wherein said force generating arrangement comprises a        selectively deployable drag inducing arrangement.    -   (BB) Wherein said force generating arrangement comprises a        selectively deployable air brake arrangement.    -   (CC) Wherein said air brake arrangement comprises a plurality of        airbrakes laterally mounted to at least one of said body and        said boom member.    -   (DD) Wherein said force generating arrangement is configured for        selectively generating a force along said boom axis in a        direction towards said nozzle responsive to said nozzle being in        predetermined proximity to the fuel receptacle of the receiver        aircraft wherein to force said nozzle into engagement with the        fuel receptacle.    -   (EE) Wherein the fuel hose is substantially non-rigid and/or        wherein said body is selectively steerable.    -   (FF) Wherein said boom member is selectively reversibly        telescopically deployable along said boom axis with respect to        said body.    -   (GG) Wherein said boom member is pivotably mounted to said body.    -   (HH) a controller configured for selectively steering the body        to an engagement enabling position spaced with respect to the        receiver aircraft and for aligning said boom axis in an        engagement enabling orientation at said spaced position, and for        subsequently moving the boom member along said boom axis towards        the receiver aircraft for enabling fuel communication        therebetween.    -   (II). A suitable communication system to transmit image data and        to receive control commands/signals. For example, the        communications system can be operatively connected to the        controller for controlling operation of the refueling device.    -   (JJ) A spatial control system configured for selectively        ensuring maintaining a desired non-zero angular disposition        between said boom axis and said forward direction at least when        said refueling device is towed by the tanker aircraft in said        forward direction via said fuel hose, and/or configured for at        least providing directional stability at least during deployment        of drag generating system, the spatial control system being        different from said force generating arrangement. The spatial        control system according to at least this aspect of the        presently disclosed subject matter can optionally comprise one        or more of features (B) to (L), optionally including one or more        of features (k1) to k(15), mutatis mutandis, in any desired        combination or permutation.    -   (KK) A coupling having a hose interface configured for        connecting said lumen to the fuel hose, said coupling configured        for allowing relative rotation between the hose and said body in        at least one degree of freedom while maintaining said fuel        communication. The coupling according to at least this aspect of        the presently disclosed subject matter can optionally comprise        one or more of features (n1) to (n4), mutatis mutandis, in any        desired combination or permutation.    -   (LL) A data acquisition system configured for providing spatial        data relating to a relative spatial disposition between said        fuel delivery nozzle and a fuel receptacle of the receiver        aircraft, to enable selectively controlling the refueling device        to provide automatic or autonomous or manual engagement of the        fuel delivery end to the fuel receptacle, said system optionally        comprising an imaging system configured for providing said data        including image data corresponding to a field of regard aft of        the refueling device, and wherein optionally said imaging system        comprises or is operatively connected to a computing system        configured for identifying a fuel receptacle of a receiver        aircraft within said field of regard from said image data, and        for determining a spatial disposition of said fuel delivery        nozzle with respect to the fuel receptacle. The data acquisition        system can be in the form of an imaging system, and can        optionally comprise one or more of features (q1) to (q6),        mutatis mutandis, in any desired combination or permutation.

According to at least one other aspect of the presently disclosedsubject matter, the refueling device comprises:

-   -   (aaa) a body configured for being towed by a tanker aircraft via        a fuel hose at least during in-flight refueling operation, and        comprising a fuel delivery lumen configured for fluid        communication with said fuel hose at least during the in-flight        refueling operation, said lumen being configured to enable fuel        to be transferred from the fuel hose to a receiver aircraft        during said in-flight refueling operation;    -   (bbb) a coupling having a hose interface configured for        connecting said lumen to the fuel hose, said coupling configured        for allowing relative rotation between the hose and said body in        at least one degree of freedom while maintaining said fuel        communication.

The refueling device according to this aspect of the presently disclosedsubject matter can optionally comprise one or more of the followingfeatures, in any desired combination or permutation:

-   -   (AAA) Wherein said coupling is configured for allowing relative        rotation between the hose and said body in at least two degrees        of freedom.    -   (BBB) Wherein said coupling is configured for allowing relative        rotation between the hose and said body in three degrees of        freedom.    -   (CCC) Wherein said body comprises a boom member having a boom        axis, and wherein said lumen is configured to enable fuel to be        transferred from the fuel hose to a receiver aircraft via said        boom member during said in-flight refueling operation, and/or at        least one said degree of freedom has the respective axis of        rotation generally orthogonal to a plane defining said non-zero        angular disposition between said boom axis and said forward        direction.    -   (DDD) Wherein said coupling comprises a universal coupling.    -   (EEE) Wherein the fuel hose is substantially non-rigid.    -   (FFF) Wherein said boom member is selectively reversibly        telescopically deployable along said boom axis with respect to        said body.    -   (GGG) Wherein said boom member is pivotably mounted to said        body.    -   (HHH) A data acquisition system configured for providing spatial        data relating to a relative spatial disposition between a fuel        delivery end of said boom member and a fuel receptacle of the        receiver aircraft, to enable selectively controlling the        refueling device to provide automatic or autonomous or manual        engagement of the fuel delivery end to the fuel receptacle, said        system optionally comprising an imaging system configured for        providing said data including image data corresponding to a        field of regard aft of the refueling device, and wherein        optionally said imaging system comprises or is operatively        connected to a computing system configured for identifying a        fuel receptacle of a receiver aircraft within said field of        regard from said image data, and for determining a spatial        disposition of said fuel delivery end with respect to the fuel        receptacle.    -   (III) A suitable communication system to transmit image data and        to receive control commands/signals. For example, the        communications system can be operatively connected to the        controller for controlling operation of the refueling device.    -   (JJJ) A spatial control system configured for selectively        ensuring maintaining a desired non-zero angular disposition        between said boom axis and said forward direction at least when        said refueling device is towed by the tanker aircraft in said        forward direction via said fuel hose, and/or, configured for at        least providing directional stability. The spatial control        system according to at least this aspect of the presently        disclosed subject matter can optionally comprise one or more of        features (B) to (L), optionally including one or more of        features (k1) to k(15), mutatis mutandis, in any desired        combination or permutation.    -   (KKK) A force generating arrangement configured for selectively        generating a force along said boom axis in a direction towards        said nozzle. The force generating arrangement according to at        least this aspect of the presently disclosed subject matter can        optionally comprise one or more of features M1 and/or M2 and/or        (m1) to (m4), mutatis mutandis, in any desired combination or        permutation.    -   (LLL) A data acquisition system configured for providing spatial        data relating to a relative spatial disposition between a fuel        delivery nozzle of the refueling device and a fuel receptacle of        the receiver aircraft, to enable selectively controlling the        refueling device to provide automatic and/or autonomous and/or        manual engagement of the fuel delivery nozzle to the fuel        receptacle of the receiver aircraft. In at least one example,        the system comprises an imaging system for providing said data        including at least image data corresponding to a field of regard        with respect to the refueling device. The data acquisition        system can be in the form of an imaging system, and can        optionally comprise one or more of features (q1) to (q6),        mutatis mutandis, in any desired combination or permutation.

According to at least one other aspect of the presently disclosedsubject matter, there is provided a refueling system comprising arefueling fuel reservoir connected to a refueling device via a hose, therefueling device being as defined in the examples herein, in particularas defined above and optionally including one or more of the featureslisted above in A to S, AA to LL, and AAA to LLL, in any desiredcombination or permutation. Optionally, the refueling system can behoused in a suitable pod configured to be fixedly attached to a tankeraircraft.

According to at least one other aspect of the presently disclosedsubject matter, there is provided a tanker aircraft comprising at leastone refueling system as defined herein, for example comprising onerefueling system as defined herein, or comprising two refueling systemsas defined herein, or comprising three refueling systems as definedherein, or comprising more four or more refueling systems as definedherein.

According to the tanker aircraft may be a manned tanker aircraft or aUAV, and/or at least one receiver aircraft may be a manned aircraft or aUAV.

Optionally, a tanker aircraft according to the presently disclosedsubject matter can comprise one or two such refueling systems mounted tothe wings (e.g. via pods) and additionally comprise one conventional“flying boom” system in the aft fuselage. Thus, it is readily apparentthat existing tanker aircraft already fitted with conventional “flyingboom” systems can be retrofitted with refueling systems according to thefirst aspect of the presently disclosed subject matter, for example onesuch refueling system fitted onto each wing, thereby effectivelytripling the refueling efficiency/capability of such a tanker aircraft,enabling up to three receiver aircraft having fuel receptacles to berefueled concurrently.

Optionally, a tanker aircraft according to the presently disclosedsubject matter can comprise one or more such refueling systems, as wellas at least one conventional “hose and drogue” system, enabling receiveraircraft of both types to be refueled concurrently.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the presently disclosed subject matter and to seehow it may be carried out in practice, examples will now be described,by way of non-limiting example only, with reference to the accompanyingdrawings, in which:

FIG. 1 is a top view of an example of a tanker system according to thepresently disclosed subject matter.

FIG. 2 is a side view of the tanker system of FIG. 1.

FIG. 3 is an isometric view of an example of a refueling deviceaccording to the presently disclosed subject matter.

FIG. 4 is a side view of the refueling device of FIG. 3.

FIG. 5 is a top view of the refueling device of FIG. 3.

FIG. 6( a) is a front view of the refueling device of FIG. 3; FIG. 6( b)is an aft view of the refueling device of FIG. 3.

FIG. 7 is a cross-sectional side view of the refueling device of FIG. 5taken along B′-B′.

FIG. 8 is a cross-sectional side view of the refueling device of FIG. 4taken along A′-A′.

FIG. 9( a) is an isometric view of the refueling device of FIG. 3, withthe airbrakes and boom member in the deployed positions; FIG. 9( b) is atop view of the refueling device of FIG. 9( a).

FIG. 10( a) is a partial side view of the example of the boom member ofthe refueling device of FIG. 3 in proximity to a fuel receptacle of areceiver aircraft; FIG. 10( b) is an alternative variation of theexample of FIG. 10( a).

FIG. 11 is an isometric view of the refueling device of FIG. 3, furtherschematically illustrating a volume aft thereof.

FIGS. 12( a) to 12(d) are respective isometric, side, top and frontviews of an alternative variation of the example of refueling device ofFIG. 3.

FIGS. 13( a) to 13(e) are respective isometric views of otheralternative variations of the example of refueling device of FIG. 3.

FIGS. 14( a) and 14(b) are respective isometric views of otheralternative variations of the example of refueling device of FIG. 3.

FIGS. 15( a) to 15(d) illustrate another alternative variation of theexample of refueling device of FIG. 3, in isometric view, top view, sideview and aft view, respectively.

FIGS. 16( a) to 16(d) illustrate another example of a refueling deviceaccording to the presently disclosed subject matter, in isometric view,side view, top view and front view, respectively.

FIGS. 17( a) to 17(e) illustrate an alternative variation of the exampleof the refueling device FIGS. 16( a) to 16(d), in isometric view (stowedconfiguration), isometric view (deployed configuration), side view(deployed configuration), front view (deployed configuration), and topview (deployed configuration), respectively; FIGS. 17( f) to 17(g)illustrate an alternative variation of the example of the refuelingdevice FIGS. 16( a) to 16(d), in isometric view, in stowed configurationand in deployed configuration, respectively; FIG. 17( h) illustratesanother alternative variation of the example of the refueling deviceFIGS. 16( a) to 16(d), in isometric view, in deployed configuration.

FIG. 18 is a block diagram schematically illustrating a system forcontrolling in-flight refueling, according to certain examples of thepresently disclosed subject matter;

FIG. 19 is a flowchart illustrating a sequence of operations carried outfor performing in-flight refueling, according to certain examples of thepresently disclosed subject matter;

FIG. 20 is a flowchart illustrating a sequence of operations carried outfor providing maneuvering commands for positioning a receiver aircraftwithin an engagement area related thereto, according to certain examplesof the presently disclosed subject matter;

FIG. 21 is a flowchart illustrating a sequence of operations carried outfor providing steering commands to a refueling device for maneuvering toan engagement enabling position, according to certain examples of thepresently disclosed subject matter;

FIG. 22 is a flowchart illustrating a sequence of operations carried outfor determining the receiver aircraft spatial disposition with respectto the engagement area related thereto, according to certain examples ofthe presently disclosed subject matter;

FIG. 23 is a flowchart illustrating a sequence of operations carried outfor determining the refueling device spatial disposition with respect tothe engagement enabling position, according to certain examples of thepresently disclosed subject matter;

FIG. 24 is an illustration of an example of a receiver aircraftpositioned outside a virtual engagement area, according to certainexamples of the presently disclosed subject matter;

FIG. 25 is an illustration of an example of a receiver aircraftpositioned inside a virtual engagement area, according to certainexamples of the presently disclosed subject matter;

FIG. 26 is an illustration of an example of a refueling device not in anengagement enabling position, according to certain examples of thepresently disclosed subject matter;

FIG. 27 is an illustration of an example of a refueling devicepositioned in an engagement enabling position, according to certainexamples of the presently disclosed subject matter;

FIG. 28 is an illustration of an example of a sensed image indicatingthat the refueling device is not positioned in an engagement enablingposition, according to certain examples of the presently disclosedsubject matter;

FIG. 29 is an illustration of an example of a sensed image indicatingthat the refueling device is positioned in an engagement enablingposition, according to certain examples of the presently disclosedsubject matter;

FIG. 30 is a partial side view of another example of a tanker systemaccording to certain examples of the presently disclosed subject matter;

FIG. 31 is a schematic illustration of an image acquisition systemaccording to certain examples of the presently disclosed subject matter;

FIG. 32 is a schematic illustration of a scene sensed the LIDAR unitaccording to certain examples of the presently disclosed subject matter;

FIG. 33 is a schematic representation of the depth and electromagneticdata relating to the boom refueling device and to the fuel receptacle ofthe receiver aircraft as acquired by the LIDAR unit according to certainexamples of the presently disclosed subject matter.

DETAILED DESCRIPTION OF THE DRAWINGS

In the drawings and descriptions set forth, identical reference numeralsindicate those components that are common to different embodiments orconfigurations.

Unless specifically stated otherwise, as apparent from the followingdiscussions, it is appreciated that throughout the specificationdiscussions utilizing terms such as “steering”, “determining”,“calculating”, “providing”, “causing”, “activating”, “receiving”,“acquiring”, “comparing”, “obtaining”, or the like, include actionand/or processes of a computer that manipulate and/or transform datainto other data, said data represented as physical quantities, e.g. suchas electronic quantities, and/or said data representing the physicalobjects. The term “computer” should be expansively construed to coverany kind of electronic device with data processing capabilities,including, by way of non-limiting example, a personal computer, aserver, a computing system, a communication device, aprocessor/processing unit (e.g. digital signal processor (DSP), amicrocontroller, a microprocessor, a field programmable gate array(FPGA), an application specific integrated circuit (ASIC), etc.), anyother electronic computing device, and or any combination thereof.

The operations in accordance with the teachings herein may be performedby a computer specially constructed for the desired purposes or by ageneral purpose computer specially configured for the desired purpose bya computer program stored in a computer readable storage medium.

As used herein, the phrase “for example,” “such as”, “for instance” andvariants thereof describe non-limiting embodiments of the presentlydisclosed subject matter. Reference in the specification to “one case”,“some cases”, “other cases”, “one example”, “some examples” or variantsthereof means that a particular feature, structure or characteristicdescribed in connection with the embodiment(s) is included in at leastone embodiment of the presently disclosed subject matter. Thus theappearance of the phrase “one case”, “some cases”, “other cases”, “oneexample”, “some examples” or variants thereof does not necessarily referto the same embodiment(s).

It is appreciated that certain features of the presently disclosedsubject matter, which are, for clarity, described in the context ofseparate embodiments, may also be provided in combination in a singleembodiment. Conversely, various features of the presently disclosedsubject matter, which are, for brevity, described in the context of asingle embodiment, may also be provided separately or in any suitablesub-combination.

In embodiments of the presently disclosed subject matter, fewer, moreand/or different stages than those shown in FIGS. 19 to 23 can beexecuted. In embodiments of the presently disclosed subject matter oneor more stages illustrated in FIGS. 19 to 23 can be executed in adifferent order and/or one or more groups of stages may be executedsimultaneously. FIGS. 7 and 18 illustrate a general schematic of thesystem architecture in accordance with an embodiment of the presentlydisclosed subject matter. Each module in FIGS. 7 and 18 can be made upof any combination of software, hardware and/or firmware that performsthe functions as defined and explained herein. The modules in FIGS. 7and 18 can be centralized in one location or dispersed over more thanone location. In other embodiments of the presently disclosed subjectmatter, the system may comprise fewer, more, and/or different modulesthan those shown in FIGS. 7 and 18.

According to a first aspect of the presently disclosed subject matter,there are provided systems and devices for in-flight refueling ofaircraft.

Referring to FIGS. 1 and 2, a tanker system according to one example ofthe presently disclosed subject matter, generally designated 10,comprises a tanker aircraft 12 comprising one or more in-flightrefueling systems 50. In this example, the tanker aircraft 12 has threesuch in-flight refueling systems 50, one comprised on each one of theport wing 14 and starboard wing 16, and a third one comprised on therear portion of the fuselage 15, and the tanker aircraft 12 isconfigured for in-flight concurrent refueling of up to three receiveraircraft 20. In alternative variations of this example the tankeraircraft 12 can have at least one, or two, or more than three in-flightrefueling systems 50, arranged in any suitable configuration withrespect to the tanker aircraft 12.

By way of non-limiting example, such a tanker aircraft 12 can be asuitably equipped Boeing 767 and each receiver aircraft 20 can includeany one of suitably equipped F-15, or F-16, or B2 stealth bomber, orother suitably equipped fighter, bomber or other aircraft.Alternatively, and also by way of non-limiting example, the tankeraircraft may be a UAV, and/or at least one of the receiver aircraft maybe a UAV.

Also by way of non-limiting example, a refueling flight envelope for usewith such a tanker system can include a forward speed of between about220 knots and about 320 knots (typically about 280 knots), and analtitude of between 500 ft and between about 30,000 ft and about 40,000ft, and in general not below about 10,000 ft, in which refueling cantake place between the tanker aircraft 12 and each receiver aircraft 20,flying in formation, depending on the operating limits of the tankeraircraft and of the receiver aircraft, as well as other factors.

Each in-flight refueling system 50 comprises an elongate, non-rigid,fuel delivery hose 52, reversibly extendible from the tanker aircraft12. A first end (not shown) of the hose 52 is connected to a refuelingfuel tank (not shown) carried by the tanker aircraft 12. For example,such a refueling fuel tank can be an internal fuel tank of the tankeraircraft 12, for example the tanker aircraft's own fuel tanks, or aspecial fuel reservoir mounted internally in the tanker aircraft 12, forexample in the fuselage, or externally and carried in fuel pods, forexample.

The hose 52 is flexible and can be retracted into a roll up drum (notshown), suitably provided in the tanker aircraft 12, and selectivelydeployed therefrom when required.

The second (aft) end 54 of hose 52 is operatively connected to arespective refueling device that is towed in a forward direction A bythe tanker aircraft 12 via hose 52 when the hose 52 is extended and thetanker aircraft 12 is in flight.

In this example, one in-flight refueling system 50 is centrally-locatedand mounted with respect to the rear fuselage of the tanker aircraft 12,and each of the other two in-flight refueling systems 50 is comprised ina respective pod 51 that is attached to the underside of the respectivewing.

FIGS. 3 to 11 illustrate a refueling device according to a first exampleof the presently disclosed subject matter, generally designated 100, foruse with an in-flight refueling system, for example at least one of thein-flight refueling systems 50 illustrated FIGS. 1 and 2.

For convenience, and referring to FIG. 3 for example, a roll axis R, apitch axis P and a yaw axis Y can be conventionally defined with respectto the refueling device 100. The roll axis R is parallel to or co-axialwith the longitudinal axis 111 of the device 100; the pitch axis P isgenerally in lateral and orthogonal relationship to the roll axis R(i.e., parallel to the horizontal when the body is at a zero rollangle); and yaw axis Y is in orthogonal relationship to the roll axis Rthe pitch axis P (i.e., parallel to the vertical when the body is at azero pitch angle).

Refueling device 100 is affixed to the end 54 of hose 52 and comprisesan elongate body 110 comprising a longitudinal axis 111 and a generaloval cross section (as best seen in FIGS. 6( a) and 6(b)), although inalternative variations of this example the body 110 can have anysuitable cross-sectional shape, for example circular cross-section,polygonal cross-section, and so on. Referring in particular to FIGS. 7and 8, the body 110 comprises a fuel delivery lumen 120 and a boommember 130 (which at least in the disclosed examples is a substantiallyrigid boom member) in fluid communication therewith. The boom member 130defines a boom axis 131 and comprises a fuel delivery nozzle 135 at aterminus 136 of the boom member 130. The nozzle 135 is configured forreversibly engaging with the fuel receptacle 22 of a receiver aircraft20 (see also FIGS. 1, 2 and 11), and thus can comprise any conventionaldesign of such nozzles, which are well known, or indeed can comprise anyother current or future design of such an in-flight refueling nozzle.

The boom member 130 is telescopically mounted to body 110, and isreversibly extendable from a stowed position illustrated in FIGS. 3 to 8in which most of the boom member 130 is accommodated in a sleeve withinthe body 110, to the fully extended position illustrated in FIGS. 9( a)and 9(b), by means of a controllable actuation mechanism (not shown).Optimally, the boom member 130 is telescopically extendable to acontrollably variable extended position in a general aft direction fromthe aft end 112 of body 110, up to the aforesaid the fully extendedposition. While in this example the boom axis 131 is parallel andco-axial with longitudinal axis 111, in at least some alternativevariations of this example the boom axis can be parallel but notco-axial with the body longitudinal axis, or the boom axis can benon-parallel with respect to the body longitudinal axis.

Thus, the boom member 130 is mounted with respect to the body 110 suchas to maintain a generally parallel spatial disposition between the boomaxis 131 and the longitudinal axis 111, at least during in-flightrefueling operation of device 100.

In an alternative variation of this embodiment, the boom member 130 ispermanently extended with respect to the body 110, and is nottelescopically or reversibly extendible therefrom. In anotheralternative variation of this example, the boom member 130 ispermanently retracted with respect to the body 110, and is nottelescopically or reversibly extendible therefrom, and thus may onlycomprise a relatively short section extending aft from the body 110 toconnect to the nozzle 135.

In alternative variations of this example, or in other examples, theboom member may have any other suitable structure configured forcoupling with the receiver aircraft, in particular the fuel receptaclethereof.

The body 110 comprises a coupling 140 at forward end 114 thereof. Thecoupling 140 comprises a hose interface 142 configured for connectingthe lumen 120 to the hose 52, and thereby to the tanker aircraft 12. Thecoupling 140 is configured for allowing relative rotation between thebody 110 and the hose 52 while maintaining fluid communication betweenthe lumen 120 and the hose 52 and thus the refueling tank. In thisexample, the coupling 140 is in the form of a universal joint or thelike (also referred to as a universal coupling, a Cardan joint, aHardy-Spicer joint or a Hooke's joint, and so on), and is thusconfigured for allowing relative rotation between the body 110 and thehose 52 in three degrees of freedom. In alternative variations of thisexample and in other examples, the coupling can instead be configuredfor allowing relative rotation between the body 110 and the hose 52 inone degree of freedom, or in two degrees of freedom. In particular, thecoupling allows the body 110, and in particular the boom member 130 andthe boom axis 131 to freely pivot with respect to the hose 52, inparticular the second end 54, about at least one axis B (see FIGS. 3 and5, for example), so that the spatial orientation of the refueling device100 can be controllably changed without significant mechanicalresistance thereto being generated by the hose 52 about axis B, which istypically parallel the pitch axis P of the refueling device 100, but maybe alternatively inclined to the pitch axis P and/or to the roll axis Rand/or to the yaw axis Y.

The body 110 can optionally be formed as an integral and/or unitarystructure incorporating the boom member 130 and the coupling 140.

In alternative variations of this example the coupling 140 can beomitted and replaced with a fixed coupling that is configured tomaintain a fixed relative spatial disposition between the body 110 andthe hose 52 while maintaining fluid communication between the lumen 120and the hose 52. For example such a spatial disposition may be an angleφ (see FIG. 1) of about 0°; or about 30°; or in a range between about 5°and about 85°; or in a range between about 10° and about 80°; or in arange between about 15° and about 70°; or in a range between about 20°and about 60°; or in a range between about 25° and about 50°; or in arange between about 20° and about 40°; or in a range between about 25°and about 40°; or in a range between about 28° and about 32°.

The refueling device 100 further comprises a spatial control system 160,configured for controlling a spatial disposition of the refueling device100 when towed aft of the tanker aircraft 12 via the hose 52, andenables the refueling device 100 to be steered and/or to adopt anydesired stable spatial disposition while being towed at the end 54 ofhose 52.

In particular, spatial control system 160 is configured for selectivelyand controllably providing a non-zero angular disposition, angle θ,between the boom axis 131 and the forward direction A, and enables thisangle θ to be selectively maintained between the boom axis 131 and theforward direction A at least for a part of the time when the refuelingdevice 100 is being towed by the tanker aircraft 12 via hose 52, inparticular during the engagement operation of the fuel device 100 to thereceiver aircraft 20 and during refueling thereof. In particular, angleθ is in pitch, i.e., about a pitch axis P of the refueling device 100and is defined on a plane including the roll axis R and the yaw axis Yof the refueling device 100. Angle θ is thus representative of an angleof attack of the refueling device 100 in the airflow, or at least of theboom axis 131 with respect to forward direction A (which is typically,but not exclusively, parallel to the horizontal direction).Nevertheless, and depending on specific conditions during any particularrefueling operation, angle θ can include an angular displacementcomponent between the boom axis 131 and the forward direction A in yaw(i.e., about yaw axis Y), for example due to sideslip angle, and/or inroll (i.e. about roll axis R), instead of or in addition to an angulardisplacement component in pitch (i.e., about pitch axis P).

The refueling device 100, in particular the boom member 130, nozzle 135and lumen 120 can be sized to allow suitable fuel flow rates forrefueling a wide range of receiver aircraft. By way of non-limitingexample, relative high fuel flow rates (for example up to 1000 USgallons/6,500 lb per minute) can be provided for refueling operations oflarge aircraft (for example transport aircraft, bombers, etc), while forfighter aircraft that cannot accept fuel at the maximum flow rate of therefueling device 100, the refueling pressure can be correspondinglyreduced. Alternatively the refueling device 100, in particular the boommember 130, nozzle 135 and lumen 120 can be sized to allow suitable fuelflow rates for refueling a narrow range of receiver aircraft, forexample only fighter aircraft or only larger aircraft (for example about400 US gallons/2,600 lb per minute).

Thus, the spatial control system 160 is configured for providingstability to the refueling device 100, while tethered to and towed bythe tanker aircraft 12 via the hose 52, and while the boom axis 131 isat any desired pitch and/or yaw and/or roll angle corresponding to theaforesaid angle θ.

In particular, and referring to FIG. 10( a) and FIG. 10( b), angle θ issuch as to provide a design angle (angle θ_(des)) that is within aparticular angular range which corresponds to the design relativeangular position of the boom member 130 (and boom axis 131) with respectto the receiver aircraft 20.

In particular, design angle θ_(des) is the design relative angularposition of the boom axis 131 with respect to the longitudinal axis ofthe receiver aircraft 20 (the receiver aircraft 20 being at apredetermined spatial orientation relative to the forward direction,typically in horizontal forward flight), to enable the boom member 130to align and engage the nozzle 135 with respect to the fuel receptacle22. Thus, angle θ (which can have an angular component in yaw and/or inpitch and/or in roll) compensates for any off-nominal pitch of thereceiver aircraft 20 (for example if the receiver aircraft 20 istraveling along direction A at a non-zero angle of attack) and/or forany off-nominal roll of the receiver aircraft 20 (for example if thereceiver aircraft 20 is traveling along direction A at a non-zero rollangle) and/or for any off-nominal yaw of the receiver aircraft 20 (forexample if the receiver aircraft 20 is traveling along direction A at anon-zero sideslip angle) to ensure that the actual angular dispositionbetween the boom axis 131 and the receiver aircraft longitudinal axis ismaintained at design angle θ_(des) even as the relative spatialorientation between the receiver aircraft 20 and the forward directionchanges.

Thus, design angle θ_(des) the boom axis 131 is in an engagementenabling orientation with respect to the receiver aircraft 20, and inparticular with respect to the fuel receptacle 22.

In non-limiting examples, angle θ (and in particular angle θ_(des)) canbe in a range between about 5° and about 85°; or in a range betweenabout 10° and about 80°; or in a range between about 15° and about 70°;or in a range between about 20° and about 60°; or in a range betweenabout 25° and about 50°; or in a range between about 20° and about 40°;or in a range between about 25° and about 40°; or in a range betweenabout 28° and about 32°.

In one non-limiting example, angle θ_(des) can be about 30°, andoperation of the refueling device 100 to adopt this angle automaticallyrenders it compatible for use with existing receiver aircraft 20, inwhich the fuel receptacles 22 are configured for receiving and engagingwith a nozzle at the end of a boom where the boom is at about 30° to thelongitudinal axis of the receiver aircraft, without the need formodifying the configuration of the fuel receptacle thereof.

Thus, when angle θ is equal to design angle θ_(des), the receiveraircraft travelling along direction A with zero angle of attack and zerosideslip and zero roll, and boom axis 131 is at the required spatialorientation to the forward direction A of the tanker aircraft and thereceiver aircraft such as to ensure engagement between the nozzle 135 inthe fuel receptacle 22, without the need for modifying the configurationof the fuel receptacle thereof.

In this example, the spatial control system 160 comprises a selectivelycontrollable aerodynamic control system 170, comprising a forward set172 of aerodynamic control surfaces 173 mounted to body 110 at a forwardportion thereof, and an aft set 174 of aerodynamic control surfaces 175mounted to the body 110 at an aft portion thereof. Referring inparticular to FIG. 4, the aft set 174 is thus in aft spaced relationshipwith respect to the forward set 172, and the center of gravity CG of thebody 110 is disposed longitudinally intermediate the aft set 174 and theforward set 172, noting that the actual longitudinal position of thecenter of gravity CG can shift between two extreme longitudinalpositions according to, inter alia, whether the boom member 135 isextended or retracted, and whether fuel is present in the refuelingdevice 100 or absent therefrom. In alternative variations of thisexample and in other examples, the center of gravity can be forward ofboth the forward set and the aft set of aerodynamic surfaces, which areconfigured to provide the required stability to the refueling device 100with the boom axis 131 at any desired pitch and/or yaw and/or rollangle.

In this example, the forward set 172 comprises four aerodynamic controlsurfaces 173 in cruciform “X” configuration (see in particular FIGS. 6(a) and 6(b)). Each aerodynamic control surface 173 is in the form of avane, pivotably mounted to the body 110 via a respective boss 183laterally projecting from the surface of body 110. Each boss 183 housesan actuator (not shown) for controlling the angular position of therespective vane about a respective pivot axis, and is controlled bycontroller 180. The pivot axes of the vanes are, in at least thisexample, orthogonal to at least one of longitudinal axis 111 and boomaxis 135, and can also intersect the respective at least one oflongitudinal axis 111 and boom axis 135.

In this example, controller 180 comprises any suitable computer controlsystem, and is housed in the refueling device 100 (see FIG. 7). Inalternative variations of this example and in other examples, thecontroller 180 or portions thereof can instead comprise any suitableelectronic control unit, or any other suitable control unit.Additionally or alternatively, the controller or portions thereof can becomprised elsewhere in the in-flight refueling system 50 or in thetanker aircraft 12.

In this example, the aft set 174 comprises two aerodynamic controlsurfaces 175 in “Vee” configuration (see in particular FIGS. 6( a) and6(b)). Each aerodynamic control surface 175 is in the form of a vane,pivotably mounted to the body 110 via a respective boss 186 laterallyprojecting from the surface of body 110. Each boss 186 houses anactuator (not shown) for controlling the angular position of therespective vane, and is also controlled by controller 180.

In this example, and referring in particular to FIG. 4, each boss 183has an aerofoil-shaped cross section defining a chord 185, and each boss186 has an aerofoil-shaped cross section defining a chord 185.Furthermore the chord 185 is oriented with respect to at least one ofthe longitudinal axis 111 and the boom axis 131 such as to align thechord 185 with the forward direction A, which is nominally the airflowdirection with respect to the refueling device 100, when the refuelingdevice 100 is at spatial orientation in which the boom axis 131 is atangle θ_(des) with respect to the forward direction A. Similarly, eachchord 185 is oriented with respect to at least one of the longitudinalaxis 111 and the boom axis 131 such as to align the chord 185 with theforward direction A when the refueling device 100 is at spatialorientation in which the boom axis 131 is at angle θ_(des) with respectto the forward direction A.

In alternative variations of this example or in other examples, theforward set aerodynamic control surfaces can comprise two or three orfour or more than four vanes (or any other type of aerodynamic controlsurfaces), in any suitable configuration, including for example fourvanes in cruciform “+” configuration, and/or, each vane (or other typeof aerodynamic control surfaces) can be pivotable about a respectiveaxis having any suitable spatial relationship with respect to thelongitudinal axis of the refueling device and/or the axis of the boommember. Additionally or alternatively, the aft set aerodynamic controlsurfaces can comprise two more than two vanes (or any other type ofaerodynamic control surfaces), in any suitable configuration.Additionally or alternatively, the respective aerodynamic controlsurfaces of the spatial control system, in the form of pivotable vanesor any other suitable configuration, are mounted to respective bosses,which can be aerodynamically shaped but at a different orientation withrespect to the longitudinal axis 111 and/or the boom axis 131, orwherein the respective bosses can have a different shape, for example inthe form of cylinders or any other prismatic shape or other shape, orwherein the respective aerodynamic control surfaces are directly mountedto the body 110 without bosses (in which case the respective actuatorscan be provided in the body 110).

For example, one such alternative variation of the refueling deviceexample of FIGS. 3 to 11 is illustrated in FIGS. 12( a) to 12(d), inwhich the respective example of the refueling device, designated 1000,comprises all the elements and features of the refueling device 100,mutatis mutandis, with the main difference that the aerodynamic controlsystem 170 of the example of the refueling device 100 is replaced withan alternative configuration for the spatial control system 160,comprising aerodynamic system 1170. Thus, the refueling device 1000comprises a body 1110, forward end 1114, aft end 1112, longitudinal axis1111, fuel delivery lumen (not shown), boom member 1130, boom axis 1131,fuel delivery nozzle 1135, terminus 1136, coupling 1140, hose interface1142, substantially similar to the corresponding components as describedherein for the example of the refueling device 100 or alternativevariations thereof, mutatis mutandis, i.e., respectively: body 110,forward end 114, aft end 112, longitudinal axis 111, fuel delivery lumen120, boom member 130, boom axis 131, fuel delivery nozzle 135, terminus136, coupling 140, hose interface 142. In addition, the refueling device1000 optionally comprises a force generating arrangement (not shown) forexample substantially similar to force generating arrangement 190 asdescribed hereinbelow, mutatis mutandis, and/or a suitable dataacquisition system (not shown) for example substantially similar toimaging system 150, as described hereinbelow, mutatis mutandis, and/or acontroller 1180, for example similar to controller 180 as describedherein, mutatis mutandis, and/or a control computer system (not shown),for example similar to control computer system 155 as described herein,mutatis mutandis.

The aerodynamic system 1170 comprises a forward set 1172 of aerodynamiccontrol surfaces 1173 mounted to body 110 at a forward end 1114 thereof,and an aft set 1174 of aerodynamic control surfaces 1175 mounted to thebody 1110 at an aft portion 1112 thereof. The aft set 1174 is thus inaft spaced relationship with respect to the forward set 1172, and thecenter of gravity of the body 1110 is disposed longitudinallytherebetween, though in alternative variations of this example and inother examples, the center of gravity can be forward or aft of both theforward set and the aft set of aerodynamic surfaces, which areconfigured to provide the required stability to the refueling device1000 with the boom axis 1131 at any desired pitch and/or yaw and/or rollangle.

In this example, the forward set 1172 comprises four aerodynamic controlsurfaces 1173 in cruciform “+” configuration, and each aerodynamiccontrol surface 1173 is in the form of a vane, pivotably mounted to thebody 1110 and operatively connected to an actuator system (not shown)for controlling the angular position of the respective vane about arespective pivot axis, and is controlled by controller 1180. The pivotaxes of the vanes are, in at least this example, orthogonal to at leastone of longitudinal axis 1111 and boom axis 1135, and can also intersectthe respective at least one of longitudinal axis 1111 and boom axis1135. In alternative variations of this example, the forward set 1172may comprise any suitable configuration or vanes, wings, RCS, etc.

In this example, the aft set 1174 comprises a high H-tail configuration,comprising two vertical stabilizers 1175, one on either side of ahorizontal stabilizer 1171, which in turn is mounted to the upper sideof the aft end 1112. Each vertical stabilizer 1175 comprises acontrollably pivotable rudder 1178, and the horizontal stabilizer 1171comprises a pair of pivotable elevators 1179, which are controllablyactuated by an actuator system (not shown) also controlled by controller1180.

For example, four other such alternative example variations areillustrated in FIG. 13( a) to FIG. 13( d), respectively, in which forthe respective refueling devices 100″a, 100″b, 100″c and 100″d,respectively, the respective forward set 172″ comprises two aerodynamiccontrol surfaces 173″ in “Vee” configuration, and the respective aft set174″ comprises two aerodynamic control surfaces 175″ in “Vee”configuration as in the first example, mutatis mutandis. In the exampleof FIG. 13( a) the aerodynamic control surfaces 173″ are smaller thanthe aerodynamic control surfaces 175″, while in the examples of FIG. 13(b) to FIG. 13 (d) the aerodynamic control surfaces 173″ are the samesize nominally as the aerodynamic control surfaces 175″. In yet otheralternative variations of the example of FIGS. 13( a) to 13(d), theaerodynamic control surfaces 173″ are larger than the aerodynamiccontrol surfaces 175″.

For example, another such alternative example variation is illustratedin FIG. 13( e), in which the respective aft set 174′ for the refuelingdevice 100′ comprises three aerodynamic control surfaces, twoaerodynamic control surfaces 175′ in “Vee” configuration as in the firstexample, mutatis mutandis, and a third vane 175″ in vertical anddownwardly depending relationship with respect to the respective body110′.

For example, two such alternative example variations are illustrated inFIGS. 14( a) and 14(b) in which the respective forward set 172′″ foreach respective refueling device 100′″a, 100′″b comprises twoaerodynamic control surfaces 173″ with zero dihedral, and the respectiveaft set 174′″ also comprises two aerodynamic control surfaces 175′″ withzero dihedral. In the example of FIG. 14( b), each aerodynamic controlsurfaces 175′″ further comprises a vertical vane 176′″ in upwardlydepending relationship with respect to the aerodynamic control surfaces175′″ at the respective wing tips.

For example, in the alternative example variations illustrated in FIGS.13( a), 13(c) and 13(d), the respective forward aerodynamic controlsurfaces 173″ are pivotably mounted to cylindrically shaped bosses 183″,and the respective aft aerodynamic control surfaces 175″ are pivotablymounted to cylindrically shaped bosses 185″. On the other hand, in theexamples illustrated in FIGS. 13( b), 14(a) and 14(b), the respectiveforward and aft aerodynamic control surfaces are pivotably mounteddirectly to the body of the respective refueling device.

Referring again to the example of FIGS. 3 to 10, the aerodynamic controlsystem 170 is configured for allowing the refueling device 100 to adoptany desired angle θ while maintaining a zero pitching moment (and/orzero yawing moment and/or zero rolling moment), as the forward set 172of aerodynamic control surfaces 173 is configured for trimming anypitching moment (and/or yawing moment and/or rolling moment,respectively) generated by aft set 174 of aerodynamic control surfaces175 at a given pitch angle (and/or yaw angle and/or roll angle,respectively) of the body 110, or vice versa. In this example, where thecenter of gravity CG is longitudinally intermediate the forward set 172and the aft set 174, the trimming pitching moment generated by theforward set 172, for example is in a counter-rotational direction withrespect to the pitching moment generated by aft set 174 to maintain aparticular pitch angle for angle θ, while the pitch forces generated byforward set 172 and the aft set 174 are in the same direction. Inalternative variations of this example or in other examples in which thecenter of gravity of the refueling device is forward of both the forwardset and the aft set of aerodynamic control surfaces, the trimmingpitching moment generated by the forward set of aerodynamic controlsurfaces, for example, is also in a counter-rotational direction withrespect to the pitching moment generated by aft set of aerodynamiccontrol surfaces to maintain a particular pitch angle for angle θ, butthe pitch forces generated by forward set of aerodynamic controlsurfaces and the aft set of aerodynamic control surfaces are in oppositedirections. In yet other examples, the refueling device comprises thespatial control system in the form of a single set of aerodynamiccontrol surfaces which are configured for generating zero pitch momentfor a desired range of pitch angles corresponding to angle θ, and thespatial control system is self-trimming to provide stable pitch anglecorresponding to angle θ.

In the first example, the aft aerodynamic control surfaces 175 arelarger than the forward aerodynamic control surfaces 173, though inalternative variations of this example and in other examples, the aftaerodynamic control surfaces 175 can be the same size or smaller thanthe forward aerodynamic control surfaces 173.

In other variations of this example and in other examples, the spatialcontrol system 160 comprises a non-adjustable aerodynamic control systemthat is configured for allowing the refueling device 100 to adopt aparticular, pre-set, desired angle θ while maintaining a zero pitchingmoment (and/or zero yawing moment and/or zero rolling moment), thisbeing the design angle θ_(des), at least at one set of conditionsassociated with the refueling—for example at a particular forward speedand altitude. Thus, once the refueling device is towed behind the tankeraircraft 12 via the hose 52, the boom axis automatically adopts theparticular design angle θ_(des), and stably maintains this relativespatial disposition at the aforesaid set of conditions until therefueling device is retracted back into the tanker aircraft 12.

In other variations of this example and in other examples, the spatialcontrol system 160 comprises a selectively controllable control systemthat is not based on aerodynamic control surfaces. For example, aplurality of suitable thrust nozzles or other suitable reaction controlthruster system (RCS) can be mounted to the body to provide thrustvector control and maintain the boom axis 131 at any desired angle θ.Such thrusters or RCS can be operatively connected to a suitablecompressed air supply or compressed gas supply, for example carried bythe refueling device itself, or carried by the tanker aircraft andsupplied to the refueling device via pneumatic or gas lines, orgenerated by the tanker aircraft and/or the refueling device using asuitable compressor taking air from the atmosphere.

Referring in particular to FIGS. 3, 4, 5, 9(a), 9(b) and 10, therefueling device 100 further comprises a force generating arrangement190. The force generating arrangement 190 is configured for selectivelygenerating a force F (FIGS. 9( a) to 11) along the boom axis 131 in adirection towards nozzle 135. In this example, the force generatingarrangement 190 selectively generates force F as a drag, and is in theform of a selectively and reversibly deployable drag inducingarrangement 192, comprising a selectively and reversibly deployable airbrake system 194. The air brake system 194 comprises a port air brake195 and a starboard air brake 196, each comprising a curved plate 197pivotably hinged laterally to the body 110 via hinges 198 between aclosed position, in which the plate is received in a recess 199 (bestseen in FIGS. 9( a) and 9(b)) and the outer surface of the plate 197 isflush with the outer surface of body 110, and an open position in whichthe plate offers a maximum frontal surface area to the airflow andthereby generates drag. The hinges 199 are forwardly disposed so thatthe convex outer surface of each one of the port air brake 195 and ofthe starboard air brake 196 faces the airflow. Suitable actuators (notshown) are operatively connected to and operate the air brakes 195, 196,controlled by controller 180. Alternatively, and as illustrated for theexample of FIG. 13( a), the hinges 199 can be disposed aft of therespective plates 197 so that the convex outer surface of each one ofthe port air brake 195 and the starboard air brake 196 faces away fromthe airflow. In the example of FIG. 13( d) the force inducingarrangement 190 is an airbrake in the form of plate 920 that isselectively laterally deployable and retractable with respect toairbrake housing 910.

The force generating arrangement 190 is in particular configured forselectively generating a force F having a magnitude sufficient forforcing the nozzle 135 into engagement with the fuel receptacle 22 ofthe receiver aircraft (FIG. 11) when the nozzle 135 (and the boom member130) and the fuel receptacle 22 are in a predetermined relative spatialdisposition, i.e., when the refueling device 100 reaches an engagementenabling position and the boom axis is in the engagement enablingorientation with respect to the receiver aircraft 20, and in particularwith respect to the fuel receptacle 22.

The force generating arrangement 190 is further configured forselectively operating in this manner responsive to the nozzle 135 beingin a predetermined proximity to the fuel receptacle 22, i.e. responsiveto the nozzle 135 being in a predetermined spacing with respect to thefuel receptacle 22, typically the engagement enabling spatial position,and can be operated manually or automatically to provide such a force F,as will become clearer herein.

Thus, at the engagement enabling position, when the boom member 130, orthe boom axis 131, is in a predetermined spatial disposition withrespect to the fuel receptacle 22 and the nozzle 135 being in apredetermined spacing with respect to the fuel receptacle 22 (i.e., atthe engagement enabling position the boom axis is at the engagementenabling orientation—corresponding to the design angle θ_(des)), theforce generating arrangement 190 can be selectively actuated to compelthe boom member 130 to follow a predetermined trajectory, for examplealigned with the boom axis 131 in the direction of the receiver aircraft20, to ensure alignment and engagement between the nozzle 135 and thefuel receptacle 22. In this example, the boom 130 is telescopicallyextended to the extended position in a direction along the boom axis131, which is maintained at the engagement enablingorientation—corresponding to the design angle θ_(des), while the body110 remains at the same spatial disposition with respect to the receiveraircraft 20. In alternative variations of this example, the boom 130 ispartially or fully telescopically extended towards the receiver aircraft20 while the device 100 can be moved towards or away from the receiveraircraft 20 to effect engagement between the nozzle 135 and the fuelreceptacle 22. In other alternative variations of this example, the boommember 130 remains retracted, and the body 110 itself is moved towardsthe receiver aircraft 20 along a the direction of the boom axis,maintaining the boom axis 131 at the engagement enablingorientation—corresponding to the design angle θ_(des), to effectengagement between the nozzle 135 and the fuel receptacle 22.

Once the nozzle 135 is forced into engagement with the fuel receptacle22 of the receiver aircraft 20, the tanker aircraft 12 can beginrefueling the receiver aircraft 20.

In alternative variations of this example and in other examples, theforce generating arrangement 190 can comprise any other suitable draginducing arrangement, for example spoilers on the vanes 175.

In yet other variations of this example and in other examples, the forcegenerating arrangement 190 can be configured for generating a thrustforce in the required direction. For example, one or a plurality ofsuitable thrust nozzles can be mounted to the body to provide therequired thrust vector parallel to the boom axis 131 towards nozzle 135.Such thrust nozzle(s) can be operatively connected to a suitablecompressed air or compressed gas supply, for example carried by therefueling device itself, or carried by the tanker aircraft and suppliedto the refueling device via pneumatic or gas lines, or generated by thetanker aircraft and/or the refueling device.

In yet other alternative variations of this example and in otherexamples, the force generating arrangement can be omitted, and forexample the receiver aircraft and/or the boom member can comprisesuitable means for mechanically engaging the nozzle to the fuelreceptacle that does not require such a force F to be generated by thedevice 100. For example, the fuel receptacle can comprise a suitablemechanical clamp that engages the terminus 136 of the boom member 130,and pulls in the nozzle 135 into engagement with the fuel receptacle 22.

Referring in particular to FIGS. 4, 5, 10 and 11 the refueling device100 further comprises a suitable data acquisition system for providingor enabling the calculation of spatial data relating to the relativespatial dispositions between the refueling device 100 and the receiveraircraft 20, in particular the relative spatial dispositions between thefuel delivery nozzle of the refueling device 100 and the fuel receptacleof the receiver aircraft, to enable selectively controlling therefueling device to provide automatic (optionally including autonomous)and/or manual steering of the refueling device 100 to the engagementenabling position and subsequent selective engagement of the fueldelivery nozzle to the fuel receptacle of the receiver aircraft. Atleast in the example of FIGS. 4, 5, and 11, the data acquisition systemis in the form of imaging system 150, in particular configured forproviding imaging data of any object coming within a field of regard(FOR) aft of the refueling device 100. Such a field of regard has apredetermined depth aft of the imaging system and in this examplecomprises sensing volume 159 aft of the imaging system 150, which whilein this example comprises a prismoidal volume in alternative variationsof this example the FOR can have any suitable shape, for exampleconical, frustoconical, cylindrical, spherical, part-spherical (e.g.hemispherical), parallelepiped (for example cubic) or any other regularor irregular shape. The sensing volume 159, i.e., the predetermineddepth of the FOR, extends aft further than is required corresponding tothe engagement enabling position, i.e., further than the maximumextension of the boom member 130 when this is in its fully deployedposition. The imaging system 150 is operatively connected to a controlcomputer system 155, which can be integral with, connected to, orindependent from controller 180 (see FIG. 8). In particular, andreferring particularly to FIGS. 10 and 11, such an object is thereceiver aircraft 20 and more particularly a part AP thereof includingthe fuel receptacle 22, and the sensing volume 159 defines an outerenvelope limit 158 in which image data of part AP can be processed,inter alia, by control computer system 155 to provide control signals,for example steering commands, to the spatial control system 160 and/orthe force generating arrangement 190, for example via controller 180 tocontrol operation of the refueling device 100, in particular therelative spatial position and orientation of the refueling device 100with respect to the receiver aircraft 20, in particular the position andorientation of the boom member 130 and nozzle 135 with respect to thefuel receptacle 22, so that the nozzle 135 can be controllably broughtinto selective engagement with the fuel receptacle 22 in a safe andeffective manner. The manner of operation of the imaging system 150 andcontrol computer system 155 will be described in greater detail furtherherein.

In this example, the imaging system 150 comprises two pairs of flashladar units 151, also referred to interchangeably herein as FLADARunits, one pair on the trailing edge of each boss 186. Suitable FLADARunits can include, for example, a PMD [Vision]® CamCube 3.0, provided byPMD Technologies, Germany, and adapted for operating within therefueling unit and at the flight conditions thereof.

In operation the FLADAR units 151 illuminate the sensing volume 159 andany object therein, in particular part AP of the receiver aircraft 20and thereafter acquire suitable image data corresponding thereto whichis sent to control computer system 155 for processing to provide theaforesaid control signals for controlling the refueling device 100. Inparticular, by means of the FLADAR units 151, a 3D image of the areas APis reconstructed, and manipulated via a computer system to determine therelative position and orientation of the nozzle 135 with respect to thefuel receptacle 22.

The sensing volume 159 thus includes the engagement enabling position.

In alternative variations of this example and in other examples, theimaging system 150 can comprise any other suitable imaging system (forexample, but not limited to, systems providing 2D images and/orstereoscopic images and/or 3D images of (including reconstruction of 3Ddata corresponding to) the sensing volume 159, in particular but notlimited to images that are updated in real time, for example in the formof a video stream) that operate to provide suitable data to the controlcomputer system 155 to, in turn, enable selectively controlling therefueling device 100 to provide autonomous and/or manual engagement ofthe nozzle 135 to the fuel receptacle 22 of the receiver aircraft 20.

In alternative variations of this example, the imaging system 150 can bereplaced with any other suitable data acquisition system for providingthe aforesaid spatial data.

In yet other alternative variations of this example and in otherexamples, the refueling device 100 can omit the imaging system 150 andcan be actively controlled by an operator, for example, to control therelative spatial position and orientation of the refueling device 100with respect to the receiver aircraft 20, in particular the spatialposition and orientation of the boom member 130 and/or nozzle 135 withrespect to the fuel receptacle 22, so that the nozzle 135 can becontrollably brought into selective engagement with the fuel receptacle22 in a safe and effective manner, for example via direct visualtracking of the device by the operator. Alternatively, the refuelingdevice can be operated as a free flying refueling device towed at theend of hose 52, and the relative spatial position and orientation of therefueling device 100 with respect to the receiver aircraft 20 (inparticular the position and orientation of the boom member 130 andnozzle 135 with respect to the fuel receptacle 22, so that the nozzlecan be controllably brought into selective engagement with the fuelreceptacle 22 in a safe and effective manner) is achieved by maneuveringthe receiver aircraft only. In such a case, the spatial control system160 can optionally comprise a non-adjustable aerodynamic stabilitysystem that is configured for allowing the refueling device 100 to adopta particular, pre-set, desired angle θ while maintaining a zero pitchingmoment (and/or zero yawing moment and/or zero rolling moment), thisbeing the design angle θ_(des) as discussed above for example.

Optionally, a suitable air-driven generator can be provided in therefueling device 100 to provide electrical power thereto. Additionallyor alternatively, electrical power can be provided to the refuelingdevice 100 by the tanker aircraft 12. Additionally or alternatively,electrical power can be provided to the refueling device 100 by one ormore batteries in the refueling device 100. Additionally oralternatively, electrical power can be provided to the refueling device100 by one or more ram air turbines (RAT), affixed internally orexternally with respect to the refueling device 100.

In at least some alternative variations of the first example therefueling device can comprise an aerodynamic stabilizer arrangement,different from the spatial control system 160 or from the forcegenerating arrangement 190. For example, each one of the alternativeexample variations illustrated in FIGS. 13( c) and 13(d) comprises suchan aerodynamic stabilizer arrangement in the form of a respective droguestructure 180″ fixed to the aft portion of the body. Such a droguestructure 180″ can be utilized for generating a drag which in turninduces a tension to the hose 52, thereby aiding reduction or dampeningof vibrations or oscillations in the hose 52 that can otherwise occur.Such a drogue structure can also be provided for other examples, forexample the first example illustrated in FIG. 3 or alternativevariations thereof.

In the example of FIGS. 15( a) to 15(d), the respective refueling device100E comprises an aerodynamic stabilizer arrangement in the form of adrogue structure 180E forwardly spaced from a forward end 114E of thefrustoconical body 110E of refueling device 100E by a length pipe 52E,which is flexible but can be articulated instead, and the body 110Ecomprises a spatial control system 160E comprising a selectivelycontrollable aerodynamic control system 170E, comprising a forward set172E of two swept back aerodynamic control surfaces 173E mounteddirectly to body 110E at a forward portion thereof, and an aft set 174Eof two aerodynamic control surfaces 175E directly mounted to the body110E at an aft portion thereof in “Vee” configuration, a deployableairbrake system 190E provided on the aft end of multi-segmentedtelescopic boom 130E, which comprises a nozzle 135E at the terminus 136Ethereof.

The in-flight refueling systems 50 including the first example of therefueling device 100 or at least some alternative variations thereof,can be operated in a number of different ways to provide selectiveengagement of the nozzle 135 with the fuel receptacle 22 of a receiveraircraft 20, and enable subsequent refueling of the receiver aircraft 20from the tanker aircraft 12 in flight, for example as disclosed herein.

Referring to FIGS. 16( a) to 16(d), a second example of the refuelingdevice, designated herein with reference numeral 200, comprises theelements and features of the first example and/or of at least somealternative variations thereof, mutatis mutandis, with some differences,as will become clearer herein, and the refueling device 200 isconfigured for use with an in-flight refueling system, for example atleast one of the in-flight refueling systems 50 illustrated FIGS. 1 and2.

For convenience, and referring to FIG. 16( a) for example, a roll axisR, a pitch axis P and a yaw axis Y can be conventionally defined withrespect to the refueling device 200. The roll axis R is parallel to orco-axial with the longitudinal axis 211 of the device 200; the pitchaxis P is generally in lateral and orthogonal relationship to the rollaxis R (i.e., parallel to the horizontal when the body is at a zero rollangle); and yaw axis Y is in orthogonal relationship to the roll axis Rthe pitch axis P (i.e., parallel to the vertical when the body is at azero pitch angle).

Refueling device 200 is affixed to the end 54 of hose 52 and comprisesbody 210 comprising a longitudinal axis 211, a fuel delivery lumen 220,and a substantially rigid boom member 230 in fluid communicationtherewith. The boom member 230 comprises a plurality of telescopicelements 232, defines a boom axis 231, and comprises a fuel deliverynozzle 235 at a terminus 236 of the boom member 230. The nozzle 235 isconfigured for reversibly engaging with the fuel receptacle 22 of areceiver aircraft 20, and thus can be similar to the nozzle 135 of thefirst example and as disclosed above, mutatis mutandis.

The boom member 230 is telescopically and pivotably mounted to body 210about axis C (generally parallel to the pitch axis P of the body 210),and is reversibly movable from a stowed position in which the telescopicelements 232 are retracted and nested in one another and the boom member230 is pivoted about axis C into a position accommodated in body 210(wherein optionally the boom axis 231 can be generally parallel tolongitudinal axis 211), to a deployed position illustrated in FIGS. 16(a) and 16(b). In the deployed position, the boom member 230 can be, bymeans of a controllable actuation mechanism (not shown), controllablyvariably extended in an aft direction from the aft end 212 of body 210,up to the fully extended position illustrated in FIGS. 16( a) and 16(b),and/or variably pivoted about pivot axis C in a downward direction toprovide a non-zero angular displacement, angle θ′, between boom axis 231and longitudinal axis 211. In this example, angle θ′ is in pitch, thoughin alternative variations of this example angle θ′ may also includeangular components in yaw and/or roll. Such angular components in yawand/or roll may be additionally provided by suitably orienting thedevice 200 with respect to the yaw axis Y and/or roll axis R,respectively. In variations of this example where the boom axis 231 canonly be pivoted with respect to the body 210 about an axis parallel tothe pitch axis P, such angular components in yaw and/or roll may bealternatively and exclusively provided by suitably orienting the device200 with respect to the yaw axis Y and/or roll axis R, respectively.

The body 210 optionally comprises a coupling 240 at forward end 214thereof, similar to the coupling 140 of the first example or alternativevariations thereof and as disclosed above, mutatis mutandis.

The refueling device 200 further comprises a spatial control system 260,configured for controlling a spatial disposition of the refueling device200 when towed aft of the tanker aircraft 12 via the hose 52. Inparticular, spatial control system 260 is configured for selectively andcontrollably providing a non-zero angular disposition, angle θ, betweenthe boom axis 231 and the forward direction A, and enables this angle θto be selectively maintained between the boom axis 231 and the forwarddirection A when the refueling device 200 is being towed by the tankeraircraft 12 via hose 52, similar to the corresponding feature of thefirst example or alternative variations thereof and as disclosed above,mutatis mutandis. Thus, in particular, angle θ is in pitch, i.e., abouta pitch axis P of the refueling device 200 and is defined on a planeincluding the roll axis R and the yaw axis Y of the refueling device200. Nevertheless, and depending on specific conditions during anyparticular refueling operation, angle θ can instead include an angulardisplacement component between the boom axis 231 and the forwarddirection A in yaw (i.e., about yaw axis Y) for example due to sideslipangle, and/or in roll (i.e. about roll axis R), in addition to anangular displacement component in pitch (i.e., about pitch axis P).

Thus, the spatial control system 260 is configured for controllablyflying the refueling device 200, and for providing stability to therefueling device 200, while tethered and towed via the hose 52, andwhile the boom axis 231 is at any desired pitch and/or yaw and/or rollangle corresponding to the aforesaid angle θ, and in particular, angle θis a design angle (angle θ_(des)) is within a particular angular rangewhich corresponds to the design relative angular position of the boommember 230 (and boom axis 231) with respect to the receiver aircraft 20similar to the corresponding feature of the first example or alternativevariations thereof and as disclosed above, mutatis mutandis.

In the second example, though, at least a part of angle θ, in particulara part of the design angle θ_(des) is provided by angle θ′, i.e., bypivoting the boom member 230 about axis C, depending on the magnitude ofangle φ, which is the relative angular disposition between thelongitudinal axis 211 and the forward direction A. The angle φ can bepositive (as illustrated in FIG. 16( b)), representing a positive angleof attack of body 210 with respect to forward direction A.Alternatively, angle φ can be negative, or zero.

In this example, the spatial control system 260 is configured forproviding a zero or near zero angle φ when the boom member 230 is in itsdeployed position pivoted at angle θ′, and comprises a selectivelycontrollable aerodynamic control system 270. The aerodynamic controlsystem 270 comprises a forward set 272 of aerodynamic control surfaces273 in the form of low aspect ratio wing members fixedly mounted to body210 at a forward portion thereof and having controllably movableailerons 271. The aerodynamic control system 270 further comprises anaft set 274 of aerodynamic control surfaces 275 mounted to the body 210at an aft portion thereof in “Vee” configuration. The spatial controlsystem 260 is also configured for providing the required pivoting angleθ′ so that angle θ′ together with angle φ provide the desired angle θbetween the boom axis 231 and the forward direction A in order tomaintain the required design angle θ_(des) between the boom axis 231 andthe longitudinal axis of the receiver aircraft 20. Thus, angle θ (whichcan have an angular component in yaw and/or in pitch and/or in roll)compensates for any off-nominal pitch of the receiver aircraft 20 (forexample if the receiver aircraft 20 is traveling along direction A at anon-zero angle of attack) and/or for any off-nominal roll of thereceiver aircraft 20 (for example if the receiver aircraft 20 istraveling along direction A at a non-zero roll angle) and/or for anyoff-nominal yaw of the receiver aircraft 20 (for example if the receiveraircraft 20 is traveling along direction A at a non-zero sideslip angle)to ensure that the actual angular disposition between the boom axis 231and the receiver aircraft longitudinal axis is maintained at designangle θ_(des) even as the relative spatial orientation between thereceiver aircraft 20 and the forward direction A changes.

In other variations of the example and in other examples, the spatialcontrol system 260 can be similar to the corresponding feature of thefirst example or alternative variations thereof and as disclosed above,mutatis mutandis.

The refueling device 200 can optionally further comprise a forcegenerating 260 arrangement (not shown), similar to the correspondingfeature of the first example or alternative variations thereof and asdisclosed above, mutatis mutandis.

The refueling device 200 can optionally further comprise a suitablespatial data acquisition system including an imaging system (not shown),similar to the corresponding feature of the first example or alternativevariations thereof and as disclosed above, mutatis mutandis, or can omitsuch an imaging system and can be actively controlled by an operator,for example, similar to the corresponding feature of the first exampleor alternative variations thereof and as disclosed above, mutatismutandis.

The in-flight refueling systems 50 including the second example of therefueling device 200, and at least some alternative variations thereof,can also be operated in a number of different ways to provide selectiveengagement of the nozzle 235 with the fuel receptacle 22 of a receiveraircraft 20, and enable subsequent refueling of the receiver aircraft 20from the tanker aircraft 12 in flight.

Referring to FIGS. 17( a) to 17(e), a variation of the second example ofthe refueling device, designated herein with reference numeral 200B,comprises the elements and features of the second example of therefueling device and/or of at least some alternative variations thereof,and/or of the first example of the refueling device and/or of at leastsome alternative variations thereof, mutatis mutandis, with somedifferences, as will become clearer herein. In a similar manner thereto,the refueling device 200B is also configured for use with an in-flightrefueling system, for example at least one of the in-flight refuelingsystems 50 illustrated FIGS. 1 and 2.

For convenience, and referring to FIG. 17( a) for example, a roll axisR, a pitch axis P and a yaw axis Y can be conventionally defined withrespect to the refueling device 200B in a similar manner to that of thesecond example of FIGS. 16( a) to 16(d), mutatis mutandis. Thus, forexample, the roll axis R is parallel to or co-axial with thelongitudinal axis 211B of the device 200B, while the pitch axis P andthe roll axis R each are in orthogonal relationship to the roll axis R.

Refueling device 200B is affixed to the end 54 of hose 52 and comprisesbody 210B in the form of an elongate fuselage and comprising alongitudinal axis 211B. The refueling device 200B also comprises asubstantially rigid boom member 230B, which defines a boom axis 231B,and comprises a fuel delivery nozzle 235B at a terminus 236B of the boommember 230B. The nozzle 235B is configured for reversibly engaging withthe fuel receptacle 22 of a receiver aircraft 20, and thus can besimilar to the nozzle 235 of the second example of nozzle 135 of thefirst example, or of alternative variations thereof, and as disclosedabove, mutatis mutandis.

In this variation of the second example, the boom member 230B has afixed axial length and is thus not extensible, providing for arelatively simple construction. However, optionally, the boom member230B can instead comprise a plurality of telescopic elements, forexample similar to the plurality of telescopic elements 232 of thesecond example of refueling device 200 illustrated in FIGS. 16( a) to16(d), mutatis mutandis.

The boom member 230B is pivotably mounted to body 210B about axis C(generally parallel to the pitch axis P of the body 210B) at pivot joint219B, and is reversibly pivotable between a stowed or retracted positionand a deployed position.

In the stowed or retracted position, illustrated in FIG. 17( a), boommember 230B is pivoted about axis C into a position where the terminus236B is closest to the underside of body 210. In this position, the boomaxis 231 is generally parallel to and displaced away from longitudinalaxis 211B in a downward direction with respect to body 210B. In thedeployed position illustrated in FIG. 17( b), boom member 230B isvariably pivoted about pivot axis C in a downward direction to provide anon-zero angular displacement, angle θ′, between boom axis 231B andlongitudinal axis 211B (best seen in FIG. 17( c). In this example, angleθ′ is in pitch with respect to the refueling device 200B.

In any case, in the retracted position, the boom axis 230B is at asmaller angular disposition with respect to said longitudinal axis 211Bthan in the deployed position. For example, in the retracted positionthe boom axis 230B is at an angular disposition with respect to saidlongitudinal axis 211B of 0°, or 15°, or between 0° and 15°, for exampleany one of 1°, 2°, 3°, 4°, 5°, 6°, 7α, 8°, 9°, 10°, 11°, 12°, 13°, 14°.For example, in the deployed position the boom axis 230B is at anangular disposition with respect to said longitudinal axis 211B ofgreater than 15°, for example 20°, or 45°, or between 20° and 40°, orbetween 20° and 45°, for example any one of 21°, 22°, 23°, 24°, 25°,26°, 27°, 28°, 29°, 30°, 31°, 32°, 33°, 34°, 35°, 36°, 37°, 38°, 39°,40°, 41°, 42°, 43°, 44°.

In general the boom member 230B is in the deployed position at leastduring in-flight refueling operation of the device 200B.

An actuation mechanism 290B is provided for controllably pivoting theboom member 230B between the stowed or retracted position and thedeployed position. Actuation mechanism 290B includes an articulatedstrut 291B comprising upper strut 292B connected to lower strut 293B atpivoting joint 294B. The upper strut 292B is pivotably connected to anunderside of body 210B, while the lower strut 293B is pivotablyconnected to an upper side of boom member 230B. An actuator (not shown)operates to selectively and effectively bring close or distance away thepivoting joint 294B with respect to the body 210B. At the maximumdistancing away of the pivoting joint 294B, illustrated in FIGS. 17( b),17(c) and 17(d), the upper strut 292B is aligned with (i.e., at about180° with respect to) the lower strut 293B, and as the pivoting joint294 is brought closer to the body 210B, the articulated strut 291Badopts a V-configuration, where the pivot angle between upper strut 292Bis and the lower strut 293B at the pivoting joint 294B progressivelyreduces from about 180° (at the fully deployed position) to about 0° (atthe stowed or retracted position). The actuator or actuation mechanism290B can be configured to selectively lock the articulated strut 291Bonly at each one of the stowed/retracted position and the deployedposition, to provide a fixed angle θ′; alternatively, the actuator oractuation mechanism 290B can be configured to selectively lock thearticulated strut 291B at each one of the stowed/retracted position andthe deployed position, and at any angular disposition therebetween, toprovide a variable angle θ′.

Other alternative configurations for actuation mechanism 290B are ofcourse possible.

Angular components in yaw and/or roll can be provided to the boom axis231B with respect to the forward direction A by suitably orienting thedevice 200B with respect to the yaw axis Y and/or roll axis R,respectively.

The boom member 230B comprises a coupling 240B at forward end 214Bthereof, fixed to the underside of body 210B. The coupling 240B issimilar to the coupling 240 of the second example or alternativevariations thereof, or of coupling 140 of the first example oralternative variations thereof, and as disclosed above, mutatismutandis. Furthermore, the pivot joint 219B can be part of coupling240B, or integrated therewith, or can be affixed thereto and/or to thebody 210. The coupling 240B is connected to the body 210B for example atthe underside of the body 210B.

The refueling device 200B further comprises a spatial control system260B and an aerodynamic stabilizer arrangement, different from thespatial control system 260B. For example, the aerodynamic stabilizerarrangement is in the form of a respective drogue structure 280B fixedto the aft portion of the body 210. Referring to FIGS. 17( a) and 17(b)respectively, the drogue structure 280B has an inactive (or stowed)configuration, in which drogue structure 280B generates minimum drag,and an active (or deployed) configuration in drogue structure 280Bgenerates more drag than in the inactive configuration, up to a maximumdrag. Such a drogue structure 280B can be utilized for generating a drag(when in the active configuration of FIG. 17( b)) which in turn inducesa tension to the hose 52, thereby aiding reduction or dampening ofvibrations or oscillations in the hose 52 that can otherwise occur.

The spatial control system 260B is configured for controlling a spatialdisposition of the refueling device 200B when towed aft of the tankeraircraft 12 via the hose 52. In particular, and in a similar manner tothe second example illustrated in FIGS. 16( a) to 16(d), mutatismutandis, spatial control system 260B is also configured for selectivelyand controllably providing a non-zero angular disposition, angle θ,between the boom axis 231B and the forward direction A, and enables thisangle θ to be selectively maintained between the boom axis 231B and theforward direction A when the refueling device 200B is being towed by thetanker aircraft 12 via hose 52, also similar to the correspondingfeature of the first example or alternative variations thereof and asdisclosed above, mutatis mutandis.

Thus, in particular, angle θ is in pitch, i.e., about a pitch axis P ofthe refueling device 200B and is defined on a plane including the rollaxis R and the yaw axis Y of the refueling device 200B. Nevertheless,and depending on specific conditions during any particular refuelingoperation, angle θ can instead include an angular displacement componentbetween the boom axis 231B and the forward direction A in yaw (i.e.,about yaw axis Y) for example due to sideslip angle, and/or in roll(i.e. about roll axis R), in addition to an angular displacementcomponent in pitch (i.e., about pitch axis P).

Thus, the spatial control system 260B is configured for controllablyflying the refueling device 200B, and for providing stability to therefueling device 200B, while tethered and towed via the hose 52, andwhile the boom axis 231B is at any desired pitch and/or yaw and/or rollangle corresponding to the aforesaid angle θ, and in particular, angle θis a design angle (angle θ_(des)) is within a particular angular rangewhich corresponds to the design relative angular position of the boommember 230B (and boom axis 231B) with respect to the receiver aircraft20 similar to the corresponding feature of the first example oralternative variations thereof and as disclosed above, mutatis mutandis.

As with the first example of the refueling device or alternativevariations thereof, or of the second example of the refueling device orother alternative variations thereof, the spatial control system 260B ofrefueling device 200B, in particular the selectively controllableaerodynamic control system 270B, is configured for enabling the device200B to be steered in one, two, or three degrees of freedom intranslation and in one, two, or three degrees of freedom in rotation,independently of the tanker aircraft 12 or of the refueling aircraft 20.Thus, the spatial control system 260B, in particular the selectivelycontrollable aerodynamic control system 270B, is configured providing:

-   -   one or more of: sideslip, up/down translation, forward-aft        translation, relative to the tanker aircraft 12 and/or to the        refueling aircraft 20, independently of rotational moments in        roll pitch and/or yaw;    -   and/or    -   rotational moments in one or more of roll pitch and/or yaw,        relative to the tanker aircraft 12 and/or to the refueling        aircraft 20, independently of sideslip, up/down translation,        forward-aft translation.

The spatial control system 260B is also configured for providing anangle of attack for the body 210B with respect to the forward direction,for example up ±10°.

In this variation of the second example of refueling device 200B,though, at least a part of angle θ, in particular a part of the designangle θ_(des) is provided by angle θ′, i.e., by pivoting the boom member230B about axis C, depending on the magnitude of the relative angulardisposition φ between the longitudinal axis 211B and the forwarddirection A, referring to FIG. 17( c). This angular disposition can bepositive, representing a positive angle of attack of body 210B withrespect to forward direction A, or can be negative, or can be zero. Inthis variation of the second example, the spatial control system 260B isconfigured for providing a zero or near zero said angular dispositionwhen the boom member 230B is in its deployed position pivoted at angleθ′.

The spatial control system 260B comprises a selectively controllableaerodynamic control system 270B. In this variation of the second exampleof the refueling device 200B, the aerodynamic control system 270Bcomprises a forward set 272B of aerodynamic control surfaces 273B and anaft set 274B of aerodynamic control surfaces 275B.

Furthermore, in the example of FIGS. 17( a) to 17(e), the a forward set272B of aerodynamic control surfaces 273B is in the form of four canards273K in cruciform “X” arrangement around a forward part of the body 210,while the aft set 274B of control surfaces 275B is in the form of aH-tail, in particular a high, cropped delta wing 276B, mounted to theupper aft part of body 210, and comprising vertical fins 277B above andbelow port and starboard wing tip elements 278B of the cropped deltawing 276B. The forward canards 273K can be fixed, or instead can bepivotable, or instead can comprise pivotable surfaces to provide controlmoments to the device 200B. The delta wing 276B, and/or vertical fins277B, are each pivotable or can instead comprise pivotable surfaces toprovide control moments to the refueling device 200B.

However, other arrangements are possible for selectively controllableaerodynamic control system 270B and/or for the body 210B.

For example the forward set 272B of aerodynamic control surfaces 273Band/or the aft set 274B of aerodynamic control surfaces 275B can each beconfigured to have any one or more of the following features, in anycombination:

-   -   monoplane configuration, including any one of: high wing        configuration (or shoulder wing configuration), low wing        configuration or mid wing configuration—mounted on or near an        upper part, a lower (bottom) part of inbetween the upper and        lower part, respectively, of the body 210; parasol wing        configuration—mounted to the body 210B via cabane struts of the        like; shoulder wing configuration;    -   biplane, triplane, quadruplane, multiplane configurations,        having two, three four, or more than four wing plane elements,        respectively, of similar size or dissimilar size with respect to        one another, stacked one above the other in unstaggered, or        forward staggered, or backwards staggered arrangement;    -   combined or closed wing configurations, in which two or more        wing elements are joined structurally at or near the respective        wing tips in some way; for example a box wing configuration, in        which at least one set of overlying (staggered or unstaggered)        wing elements is joined together between their tips by vertical        fins; tandem box wings; rhomboidal wings in which at least one        set of overlying wing elements has a forward swept wing plane        and a swept back wing plane, joined between the tips directly or        via a vertical fins; annular or ring wing, which can be flat (in        the form of the rim of a flat disc) or cylindrical (the wing is        shaped as a cylinder), for example;    -   at least one wing element is cantilevered (self-supported)        and/or externally supported to the body 210 via struts and/or        braces;    -   wings elements, wherein each can comprise low aspect ratio,        moderate aspect ratio or high aspect ratio;    -   wings elements, wherein each wing element can be swept forward        or swept back or have zero sweep, and/or the sweep angle can be        fixed or varied along the span, and/or each wing element can        have fixed wing geometry or variable wing geometry, for example        variable sweep or oblique wing configurations;    -   wings elements, wherein each wing element can have a respective        wing chord that can be fixed or varied along the span of the        wing element, for example including at least one of the        following plan shapes: elliptical plan; constant chord plan,        tapered plan; trapezoidal plan; reverse tapered plan; compound        tapered plan;    -   wings elements, wherein each wing element can be based on a        delta design, including at least one of the following: regular        delta; cropped delta (wing tip is cropped) compound delta;        double delta; ogival delta;    -   wings elements, wherein each wing element can have dihedral or        anhedral angle;    -   wings elements, wherein the wing elements can be formed as fins,        for example in cruciform “X” or cruciform “+” configuration, or        having one, two, three, four, or more than four fins arranged on        the body 210B in any geometrical arrangement;    -   wings elements, wherein the wing elements can comprise vertical        fins or the like, attached on the upper part and/or the lower        part at any spanwise position including the tip; and/or the fins        can be swept forward or swept back or have zero sweep, and/or        sweep angle can be fixed or varied along the span, and/or each        vertical fin can have fixed wing geometry or variable wing        geometry, for example variable sweep or oblique wing        configurations;    -   each wing element can be fixed, or can be movably mounted to the        body 210 and fully pivotable to operate independently as an        integral control surface, or can be fixedly mounted to the body        210 and comprises a pivotal control surface;    -   each wing element can be movably mounted to the body 210 to        allow for selective relative translational movement        therebetween.

For example the forward set 272B of aerodynamic control surfaces 273Bcan have any suitable configuration regarding its geometrical andspatial relationship with respect to the aft set 274B of aerodynamiccontrol surfaces 275B, for example as follows:

-   -   conventional configuration, in which the forward set 272B of        aerodynamic control surfaces 273B forms the main lift-generating        wing arrangement of the device 200B, while the aft set 274B of        aerodynamic control surfaces 275B, forms part of the stabilizer        or tail;    -   canard configuration, in which the aft set 274B of aerodynamic        control surfaces 275B forms the main lift-generating wing        arrangement of the device 200B, while the forward set 272B of        aerodynamic control surfaces 273B can be in the form of canards        or fins as the stabilizer;    -   tandem configuration, in which both the aft set 274B of        aerodynamic control surfaces 275B and the forward set 272B of        aerodynamic control surfaces 273B are configured to provide lift        and to provide stability;    -   tailess configuration, in which the forward set 272B of        aerodynamic control surfaces 273B is omitted, and the aft set        274B of aerodynamic control surfaces 275B is configured to        provide lift and to provide stability;    -   three-surface or triplet configuration, in which in which the        aft set 274B of aerodynamic control surfaces 275B forms the main        lift-generating wing arrangement of the device 200B, while the        forward set 272B of aerodynamic control surfaces 273B can be in        the form of canards or fins forming part of the stabilizer, and        further comprising a third set of aerodynamic control surfaces        aft of the aft set 274B of aerodynamic control surfaces 275B,        forms part of the stabilizer.

For example the forward set 272B of aerodynamic control surfaces 273Band/or the aft set 274B of aerodynamic control surfaces 275B can beblended with the body 210B to provide a blended body configuration.

For example one of the forward set 272B of aerodynamic control surfaces273B and/or the aft set 274B of aerodynamic control surfaces 275B can beomitted, and the other one of forward set 272B of aerodynamic controlsurfaces 273B and/or the aft set 274B of aerodynamic control surfaces275B can be formed as a flying wing configuration, incorporating thereinthe functions of body 210B, which can then be omitted.

For example the forward set 272B of aerodynamic control surfaces 273Band/or the aft set 274B of aerodynamic control surfaces 275B can both beomitted, and the body 210 can be formed as a lifting body, integrallyproviding the functions of the aerodynamic control system 270B.

For example, the aerodynamic control system 270B can be replaced with orsupplemented by reaction control thrusters.

Thus, for example, and referring to FIGS. 17( f) and 17(g), theaerodynamic control system 270B comprises a canard configuration, inwhich: the forward set 272B of aerodynamic control surfaces comprisescanards, for example comprising two horizontal, swept, zero tapercanards 273C in mid-wing configuration, one on each side of the body210B, and optionally including vertical swept-back zero taper fins 273Dabove and/or below the canards 273C at the respective tips thereof; theaft set 274B of aerodynamic control surfaces can be in the form of aH-tail, in particular comprising two horizontal, swept, zero-taper wingelements 273E in high-wing configuration, on the upper part of the body210B, and optionally including fins, for example vertical swept-backzero taper fins 273F above and below the wing elements 273E at therespective tips thereof. In this example, one or more of the canards273C, fins 273D, wing elements 273E and fins 273F, is fully pivotable tooperate independently as an integral control surface or is fixedlymounted to the body 210 and comprises a pivotal control surface.Optionally, one or more of the canards 273C, fins 273D, wing elements273E and fins 273F, can be movably mounted to the body 210 to allow forselective relative translational movement therebetween.

In another example, and referring to FIG. 17( h), the aerodynamiccontrol system 270B comprises a canard configuration, in which: theforward set 272B of aerodynamic control surfaces comprises a canardconfiguration, for example comprising two horizontal, swept, zero tapercanards 273C in mid-wing configuration, one on each side of the body210B, and optionally including vertical swept-back zero taper fins 273Dabove and below the canards 273C at the respective tips thereof; the aftset 274B of aerodynamic control surfaces can be in the form of a H-tail,in particular comprising two horizontal, swept, zero-taper wing elements273G in mid-wing configuration, one on each side of the body 210B, andoptionally including fins, for example vertical swept-back zero taperfins 273H above and below the wing elements 273G at the respective tipsthereof. In this example, one or more of the canards 273C, fins 273D,wing elements 273G and fins 273H, is fully pivotable to operateindependently as an integral control surface or is fixedly mounted tothe body 210 and comprises a pivotal control surface. Optionally, one ormore of the canards 273C, fins 273D, wing elements 273G and fins 273H,can be movably mounted to the body 210 to allow for selective relativetranslational movement therebetween.

It is to be noted that in other variations of the second example, and inother examples, of the refueling device 200, the respective spatialcontrol system 260 can be similar to the spatial control system 260B thevariation of the example of the refueling device 200B or alternativevariations thereof and as disclosed above, mutatis mutandis.

The refueling device 200B can optionally further comprise a forcegenerating arrangement (not shown), similar to the corresponding featureof the first example or alternative variations thereof and as disclosedabove, mutatis mutandis, and/or can be operated in a correspondingmanner.

In the variations of the second example illustrated in FIGS. 17( a) to17(h), a respective force generating arrangement 295B is configured forselectively generating a force FB (see FIG. 17( c)) along the boom axis231B in a direction towards nozzle 235B.

In these variations of the second example, the force generatingarrangement 290B comprises (a) at least some elements of the spatialcontrol system 260B, in particular the selectively controllableaerodynamic control system 270B; and optionally (b) at least someelements of the aerodynamic stabilizer arrangement, in particular in theform of a respective drogue structure 280B.

The force generating arrangement 290B is configured for selectivelygenerating force FB in a direction aligned with the boom axis 231B bygenerating a negative lift force LF (or reducing the lift force by forceLF) and a drag force LD, which together provide force FB of the requiredmagnitude and vector. The negative lift force LF can be generated bysuitably controlling the spatial control system 260B, in particular theselectively controllable aerodynamic control system 270B. For example,appropriately changing an angle of attack, and/or providing a flap angleto the respective control surfaces of the control system 270B can reducethe lift generated by the control system 270B, and thus result in a netdownwards force corresponding to negative lift force LF. Concurrently,in at least some cases, the drag force LD can also be generated bysuitably controlling the spatial control system 260B, in particular theselectively controllable aerodynamic control system 270B. For example,appropriately changing an angle of attack, and/or providing a flap angleto the respective control surfaces of the control system 270B can alsochange the drag generated by the control system 270B, and thus result inan increase in drag corresponding to drag force LD. Additional dragforce can be generated, where necessary to complement or replace thedrag generated by the control system 270B to provide the appropriatedrag force LD, by controlling the drag generated by the aerodynamicstabilizer arrangement, in particular in by the drogue structure 280B.

The force generating arrangement 295B is in particular configured forselectively generating a force FB having a magnitude sufficient forforcing the nozzle 235B into engagement with the fuel receptacle 22 ofthe receiver aircraft when the nozzle 295B (and the boom member 230B)and the fuel receptacle 22 are in a predetermined relative spatialdisposition, i.e., when the refueling device 200B reaches an engagementenabling position and the boom axis 231B is in the engagement enablingorientation with respect to the receiver aircraft 20, and in particularwith respect to the fuel receptacle 22.

The force generating arrangement 295B is further configured forselectively operating in this manner responsive to the nozzle 235B beingin a predetermined proximity to the fuel receptacle 22, i.e. responsiveto the nozzle 235B being in a predetermined spacing with respect to thefuel receptacle 22, typically the engagement enabling spatial position,and can be operated manually or automatically to provide such a forceFB, as will become clearer herein.

Thus, at the engagement enabling position, when the boom member 230B, orthe boom axis 231B, is in a predetermined spatial disposition withrespect to the fuel receptacle 22 and the nozzle 235B being in apredetermined spacing with respect to the fuel receptacle 22 (i.e., atthe engagement enabling position the boom axis is at the engagementenabling orientation—corresponding to the design angle θ_(des)), theforce generating arrangement 295 can be selectively actuated to compelthe boom member 230B to follow a predetermined trajectory (together withthe device 200B), for example aligned with the boom axis 231B in thedirection of the receiver aircraft 20, to ensure alignment andengagement between the nozzle 234B and the fuel receptacle 22. In thisexample, the boom member 230B (and thus the boom axis 231B) ismaintained at the engagement enabling orientation—corresponding to thedesign angle θ_(des), while the body 210B remains at the same spatialdisposition with respect to the receiver aircraft 20. The body 210B ismoved towards the receiver aircraft 20 along a the direction of the boomaxis 231B, maintaining the boom axis 231B at the engagement enablingorientation—corresponding to the design angle θ_(des), to effectengagement between the nozzle 235B and the fuel receptacle 22. Inalternative variations of this example, the boom 230B is telescopic, andis partially or fully telescopically extended towards the receiveraircraft 20 while the device 200B can be moved towards or away from thereceiver aircraft 20 to effect engagement between the nozzle 235B andthe fuel receptacle 22.

Once the nozzle 235B is forced into engagement with the fuel receptacle22 of the receiver aircraft 20, the tanker aircraft 12 can beginrefueling the receiver aircraft 20.

In alternative variations of this example and in other examples, theforce generating arrangement 295B can comprise any other suitable draginducing arrangement, for example spoilers on the boom member 230 and/oron other parts of the device 200B.

In yet other variations of this example and in other examples, the forcegenerating arrangement 295B can be configured for generating a thrustforce in the required direction. For example, one or a plurality ofsuitable thrust nozzles can be mounted to the body 210B and/or to theboom member 230B to provide the required thrust vector parallel to theboom axis 231B towards nozzle 235B. Such thrust nozzle(s) can beoperatively connected to a suitable compressed air or compressed gassupply, for example carried by the refueling device itself, or carriedby the tanker aircraft and supplied to the refueling device viapneumatic or gas lines, or generated by the tanker aircraft and/or therefueling device.

In yet other alternative variations of this example and in otherexamples, the force generating arrangement can be omitted, and forexample the receiver aircraft and/or the device 200B can comprisesuitable means for mechanically engaging the nozzle 235B to the fuelreceptacle that does not require such a force FB to be generated by thedevice 200B. For example, the fuel receptacle and/or the boom member230B can comprise a suitable mechanical clamp that engages the terminus236B of the boom member 230B to the fuel receptacle 22, and pulls in thenozzle 235B into engagement with the fuel receptacle 22.

The device 200B comprises controller 285B for controlling operation ofone or more of the force generating arrangement 290B, the spatialcontrol system 260B (in particular the selectively controllableaerodynamic control system 270B), the aerodynamic stabilizer arrangement(in particular in the form of a respective drogue structure 280B), forexample similar to controller 180 as described herein, mutatis mutandis,and thus for example comprises any suitable computer control system, andcan be internally or externally mounted in the refueling device 200B. Inalternative variations of this example and in other examples, thecontroller 285B or portions thereof can instead comprise any suitableelectronic control unit, or any other suitable control unit, and/or thecontroller 285B or portions thereof can be comprised elsewhere in thein-flight refueling system 50 or in the tanker aircraft 12.

The refueling device 200B further comprises a suitable spatial dataacquisition system, also referred to herein as a data acquisition system299B for providing or enabling the calculation of spatial data relatingto the relative spatial dispositions between the refueling device 200Band the receiver aircraft 20, in particular the relative spatialdispositions between the fuel delivery nozzle 235B of the refuelingdevice 200B and the fuel receptacle of the receiver aircraft, to enableselectively controlling the refueling device to provide automatic(optionally including autonomous) and/or manual steering of therefueling device 200B to the engagement enabling position and subsequentselective engagement of the fuel delivery nozzle to the fuel receptacleof the receiver aircraft.

In this variation of the second example of the device 200B, the dataacquisition system is in the form of imaging system 289B, in particularconfigured for providing imaging data of any object coming within afield of regard (FOR) aft of the refueling device 200B.

The imaging system 289B is operatively connected to a control computersystem 255B, for example similar to control computer system 155 asdescribed herein, mutatis mutandis, and which can be integral with,connected to, or independent from controller 285B. In particular, andreferring particularly to FIG. 17( b), such an object is the receiveraircraft 20 and more particularly a part AP thereof including the fuelreceptacle 22, and the sensing volume 259B defines an outer envelopelimit 258B in which image data of part AP can be processed, inter alia,by control computer system 255B to provide control signals, for examplesteering commands, to the spatial control system 260B and/or the forcegenerating arrangement 290B, for example via controller 285B to controloperation of the refueling device 200B, in particular the relativespatial position and orientation of the refueling device 200B withrespect to the receiver aircraft 20, in particular the position andorientation of the boom member 230B and nozzle 235B with respect to thefuel receptacle 22, so that the nozzle 235B can be controllably broughtinto selective engagement with the fuel receptacle 22 in a safe andeffective manner. The manner of operation of the imaging system 289B andcontrol computer system 255B will be described in greater detail furtherherein.

In alternative variations of this example, the imaging system 289B canbe replaced with any other suitable data acquisition system forproviding the aforesaid spatial data.

In yet other alternative variations of this example and in otherexamples, the refueling device 200B can omit the imaging system 289B andcan be actively controlled by an operator, for example, to control therelative spatial position and orientation of the refueling device 200Bwith respect to the receiver aircraft 20, in particular the spatialposition and orientation of the boom member 230B and/or nozzle 235B withrespect to the fuel receptacle 22, so that the nozzle 235B can becontrollably brought into selective engagement with the fuel receptacle22 in a safe and effective manner, for example via direct visualtracking of the device by one or more operators (for example, anoperator can be in the tanker aircraft 12 and/or an operator can be inthe refueling aircraft 20). Alternatively, the refueling device can beoperated as a free flying refueling device towed at the end of hose 52,and the relative spatial position and orientation of the refuelingdevice 200B with respect to the receiver aircraft 20 (in particular theposition and orientation of the boom member 230B and nozzle 235B withrespect to the fuel receptacle 22, so that the nozzle can becontrollably brought into selective engagement with the fuel receptacle22 in a safe and effective manner) is achieved by maneuvering thereceiver aircraft 20 only. In such a case, the spatial control system260B can optionally comprise a non-adjustable aerodynamic stabilitysystem that is configured for allowing the refueling device 200B toadopt a particular, pre-set, desired angle θ while maintaining a zeropitching moment (and/or zero yawing moment and/or zero rolling moment),this being the design angle θ_(des) as discussed above for example.

Optionally, a suitable air-driven generator can be provided in therefueling device 200B to provide electrical power thereto. Additionallyor alternatively, electrical power can be provided to the refuelingdevice 200B by the tanker aircraft 12. Additionally or alternatively,electrical power can be provided to the refueling device 200B by one ormore batteries in the refueling device 200B. Additionally oralternatively, electrical power can be provided to the refueling device200B by one or more ram air turbines (RAT), affixed internally orexternally with respect to the refueling device 200B.

In this variation of the second example of device 200B, the imagingsystem 289B is for example similar to imaging system 350 as describedherein, mutatis mutandis, and comprises one or more Light Detection AndRanging (LIDAR) units 351, for example similar as described herein,mutatis mutandis, which can utilize eye-safe laser. The imaging system350 in this example is located on the underside of the body 210B nearthe nose of body 210B, but in alternative variations of this example theimaging system 289B can be located elsewhere on the device 200B, forexample the at 289B′, near the tail of the body 201B, or on the spatialcontrol system 260B, so long as the respective sensing volume 359extends beyond the position of the nozzle 235B to include the nozzle235B, and part AP of the receiver aircraft 20 when the part AP is inclose proximity to the nozzle 235B.

In alternative variations of this example, the LIDAR unit 351 can bereplaced with any other suitable imaging system 350 that provides depthdata and electromagnetic intensity data of objects within the sensingvolume 359 (including, but not limited to, Flash LADAR, 3D Flash LIDARCamera, etc.). In still further alternative variations of this example,the LIDAR unit 351 can be replaced with other suitable imaging systemssuch as stereoscopic cameras, conventional cameras, various radarsystems, etc.

In any case, the control computer system 355, included in controller285B and/or controller 255B for example, comprises a memory includinggeometrical data of the shape of at least part of the receiver aircraft20, in particular part AP and or the fuel receptacle 22. The controlcomputer system 355 is further configured for operating on the depthdata and the geometrical data to enable identification of a first partof the depth data that corresponds to the part AP and or the fuelreceptacle 22.

According to certain examples of the presently disclosed subject matterthe data acquisition system 299B further includes fuel receptacle marker342, comprised on the receiver aircraft 20 in a pre-determined locationwith respect to the fuel receptacle 22 thereof. The fuel receptaclemarker 342 is at a fixed and known geometrical relationship with respectto the fuel receptacle 22, and is electromagnetically visible to theimaging system 350, at least during operation thereof.

In this example, the fuel receptacle marker 342 comprises aretro-reflective surface that reflects incident beams along the samepath, and thus provides a strong intensity reflection of the respectivereflected beam when illuminated by a beam, as compared with thereflection intensity obtained from other surfaces of the receiveraircraft 20, for example. Such a retro-reflective surface may beprovided via a retro-reflective material affixed to a certain knownlocation visible to the imaging system 350 on the receiver aircraft 20.Such retro-reflective materials are well known in the art, and caninclude for example retro-reflective tape or retro-reflective paint.

It is to be noted that the data acquisition system 299B can include anyone of the boom tip marker 340 and the fuel receptacle marker 342, or acombination of both. Alternatively, in some cases, the data acquisitionsystem 299B can include none of the markers (in this case the naturalreflective properties of the surfaces can be used).

The control computer system 355 is further configured for operating onthe depth data and the electromagnetic intensity data, as disclosedherein, mutatis mutandis, to enable identification of a second part ofthe depth data that corresponds to the high intensity reflectionoriginating from the boom tip marker 340, which in turn enablesidentification of the part of a third depth data that corresponds tonozzle 316 since the relative spatial relationship between the boom tipmarker 340 and nozzle 316 is known.

Accordingly, when the aforesaid first part and second part (first partand third part) of the depth data is known, the control computer system355 can determine the relative disposition between the boom system 300,and in particular the nozzle 316, and the receiver aircraft 20, inparticular the fuel receptacle 22 thereof.

The in-flight refueling systems 50 including this alternative variationof the second example of the refueling device 200B, and at least somealternative variations thereof, can also be operated in a number ofdifferent ways to provide selective engagement of the nozzle 235B withthe fuel receptacle 22 of a receiver aircraft 20, and enable subsequentrefueling of the receiver aircraft 20 from the tanker aircraft 12 inflight, for example as disclosed herein for the first example oralternative variations thereof, or the second example, mutatis mutandis.

Referring to FIG. 30, a tanker system according to another example ofthe presently disclosed subject matter, generally designated 10′,comprises a tanker aircraft 12′ comprising an aircraft-fixed flying boomsystem, designated by the reference numeral 300, and may optionallyfurther comprise one or more non-aircraft-fixed in-flight refuelingsystems. For example, each non-aircraft-fixed in-flight refueling systemcan comprise an in-flight refueling system 50 as disclosed above withreference to FIGS. 1 to 29, mutatis mutandis. For example, the tankeraircraft 12 can have two such in-flight refueling systems 50, onecomprised on each one of the port wing and starboard wing, and, togetherwith the fixed flying boom system 300, the tanker aircraft 12′ isconfigured for in-flight concurrent refueling of up to three receiveraircraft 20. In yet other alternative variations of this example thetanker aircraft 12′ can have no such in-flight refueling systems 50, orat least one, or two, or more than three in-flight refueling systems 50,arranged in any suitable configuration with respect to the tankeraircraft 12′.

The fixed flying boom system 300 comprises a refueling device in theform of telescoping boom fuelling unit 310, which comprises a spatialcontrol system including at least one of a mechanical connection 320 anda motion control system 330.

The boom fuelling unit 310 is movably affixed at its forward end to anunderside of the aft end of the fuselage of the tanker aircraft 12′ viathe mechanical connection 320, such as for example an articulationjoint, gimbals, and so on. The mechanical connection 320 is configuredfor providing the boom fuelling unit 310 with two rotational degrees offreedom about the yaw and pitch axes at mechanical connection 320,relative to the tanker aircraft 12′.

The boom fuelling unit 310 comprises an elongate boom member 312, and atelescoping aft section 314 configured for being selectivelytelescopically deployed and selectively telescopically retracted intoboom member 312, along boom axis 311, under the control of controller390 (that in some cases can be controller 180 or part thereof),providing the boom system 300 with a translational degree of freedomwith respect to the tanker aircraft 12′. At the boom tip or terminus ofaft section 314, the boom fuelling unit 310 comprises a fuel deliverynozzle module 317 including fuel delivery nozzle 316, which is inselective fuel communication, via a hose, pipe and so on (not shown),with a refueling fuel tank (not shown) carried by the tanker aircraft12′. The nozzle 316 is configured for reversibly engaging with the fuelreceptacle 22 of a receiver aircraft 20 (in a similar manner to theexamples illustrated in FIGS. 1 to 29 disclosed herein, mutatismutandis), and thus can comprise any conventional design of suchnozzles, which are well known, or indeed can comprise any other currentor future design of such an in-flight refueling nozzle.

The boom fuelling unit 310 further comprises motion control system 330configured for controlling the position of the boom fuelling unit 310 inelevation and azimuth, i.e., about the pitch and yaw axes at mechanicalconnection 320. In this example, the motion control system 330 comprisesaerodynamic lift/control surfaces, also known as ruddevators 325,operatively connected to controller 390. While in this and otherexamples ruddevators 325 can be in a V-tail type configuration, in yetother alternative variations of this example the aerodynamiclift/control surfaces can have any other suitable configuration.Selectively and controllably changing the incidence angles of theruddevators 325 via controller 390 generates aerodynamic forces thatenable the boom fuelling unit 310 to be aligned or aimed in anyparticular direction within a predefined envelope. Additionally oralternatively, the motion control system 330 comprises reaction controlthrusters, which can also be operatively connected to controller 390.

In particular, motion control system 330 is configured for selectivelyand controllably providing a non-zero angular disposition, angle θ,between the boom axis 311 and the longitudinal axis of the receiveraircraft 20.

The boom system 300, in particular the nozzle 316 can be sized to allowsuitable fuel flow rates for refueling a wide range of receiveraircraft. By way of non-limiting example, relative high fuel flow rates(for example up to 1000 US gallons/6,500 lb per minute) can be providedfor refueling operations of large aircraft (for example transportaircraft, bombers, etc), while for fighter aircraft that cannot acceptfuel at the maximum flow rate of the boom system 300, the refuelingpressure can be correspondingly reduced. Alternatively the boom system300 can be sized to allow suitable fuel flow rates for refueling anarrow range of receiver aircraft, for example only fighter aircraft oronly larger aircraft (for example about 400 US gallons/2,600 lb perminute).

In operation of boom system 300, angle θ can be chosen such as to be anominal design angle (angle θ_(des)) that is within a particularallowable angular range which corresponds to the range of relativeangular positions of the boom system 300 (and boom axis 311) withrespect to the receiver aircraft 20, which allow for engagement betweenthe nozzle 316 and the fuel receptacle 22.

In practice, the actual pitch, roll and yaw angles of the boom axis (andthe extension of the telescoping aft section 314 with respect to boommember 312) determine the spatial position of the boom tip including thenozzle 316 with respect to the tanker aircraft 12′. In order to allowfor engagement, the boom tip including the nozzle 316 needs to be withinthe respective refueling geometrical envelope and this position needs tobe matched with the position of receptacle 22 of the receiver aircraft20. The refueling geometrical envelope represents the safe limits ofmovement for the boom fuelling unit 310 with respect to the receiveraircraft 20 and within which contact between the receiving aircraft 20and the boom fuelling unit 310 is permitted, and can correspond to atleast part of the sensing volume 359. This position for the boom tipincluding the nozzle 316 can be achieved by adjusting angular alignmentof the boom axis in elevation and azimuth, i.e., about the pitch and yawaxes at mechanical connection 320, together with axial extension alongthe boom axis via extension/retraction of the telescoping aft section314 with respect to boom member 312. Thus, at a particular engagementenabling position, the boom tip and nozzle 316 can be positioned closeto the receptacle 22, with the boom axis being aligned at an angle θwhich can deviate from the nominal design angle (angle θ_(des)) by aallowable angular clearance (+Δθ, −Δθ), but nevertheless still withinthe aforesaid allowable angular range (angle θ_(max) to angle θ_(min)).The structure of the nozzle 316 and the receptacle 22 can be such as toallow for such deviations of angle θ from angle θ_(des) within theaforesaid allowable angular range. For example, the nozzle 316 canincorporate a ball joint and the receptacle 22 can include a funnelguide for the nozzle 316 to provide the allowable angular clearance(+Δθ, −Δθ), for example in a similar manner to that schematicallyillustrated in FIG. 10( b) regarding other examples, mutatis mutandis.By way of non-limiting example, where the nominal design angle θ_(des)is +30 degrees, engagement between the nozzle 316 and receptacle 22 canoccur even when the boom axis has an angle of +40 degrees in elevationand +8 degrees in azimuth, assuming that the nozzle 316 can engage withthe receptacle 22 with a relative spatial disposition therebetween of−10 degrees in elevation and −8 degrees in azimuth.

In at least some cases, angle θ (which can have an angular component inyaw and/or in pitch and/or in roll) can be further compensated for anyoff-nominal pitch of the receiver aircraft 20 (for example if thereceiver aircraft 20 is traveling along direction A at a non-zero angleof attack) and/or for any off-nominal roll of the receiver aircraft 20(for example if the receiver aircraft 20 is traveling along direction Aat a non-zero roll angle) and/or for any off-nominal yaw of the receiveraircraft 20 (for example if the receiver aircraft 20 is traveling alongdirection A at a non-zero sideslip angle) to ensure that the actualangular disposition between the boom axis 311 and the receiver aircraftlongitudinal axis is maintained at design angle θ_(des) even as therelative spatial orientation between the receiver aircraft 20 and theforward direction changes. Such compensation can be achieved, forexample, by steering the tanker aircraft 12′ in a corresponding manner.

Thus, at the design angle θ_(des) (and for other angles θ within theaforesaid allowable angular range (angle θ_(max) to angle θ_(min))) theboom axis 311 is in an engagement enabling orientation with respect tothe receiver aircraft 20, and in particular with respect to the fuelreceptacle 22.

In non-limiting examples, angle θ (and in particular angle θ_(des)) canbe any suitable angle in a range between about 5° and about 85°; or in arange between about 10° and about 80′; or in a range between about 15°and about 70°; or in a range between about 20° and about 60°; or in arange between about 25° and about 50°; or in a range between about 20°and about 40°; or in a range between about 25° and about 40°; or in arange between about 28° and about 32°.

In one non-limiting example, angle θ_(des) can be about 30°, andoperation of the boom system 300 to adopt this angle automaticallyrenders it compatible for use with existing receiver aircraft 20, inwhich the fuel receptacles 22 are configured for receiving and engagingwith a nozzle at the end of a boom where the boom is at about 30° to thelongitudinal axis of the receiver aircraft, without the need formodifying the configuration of the fuel receptacle thereof.

Thus, when angle θ is equal to design angle θ_(des), or within theaforesaid allowable angular range (angle θ_(max) to angle θ_(min)), thereceiver aircraft travelling along direction A with zero angle of attackand zero sideslip and zero roll, and boom axis 311 is at the requiredspatial orientation to the forward direction A of the tanker aircraftand the receiver aircraft such as to ensure engagement between thenozzle 316 in the fuel receptacle 22, without the need for modifying theconfiguration of the fuel receptacle thereof.

The boom system 300 further comprises a suitable data acquisition system360 for providing or enabling the calculation of spatial data relatingto the relative spatial dispositions between the boom system 300 and thereceiver aircraft 20, in particular the relative spatial dispositionsbetween the fuel delivery nozzle module 317 including fuel deliverynozzle 316 of the boom system 300, and the fuel receptacle 22 of thereceiver aircraft, to enable selectively controlling the boom system 300to provide automatic (optionally including autonomous) and/or manualalignment of the boom system 300 in the engagement enabling position andsubsequent selective engagement of the fuel delivery nozzle to the fuelreceptacle of the receiver aircraft.

In this example the data acquisition system 360 includes imaging system350, in particular configured for providing imaging data of any objectcoming within a field of regard (FOR), in particular the fuel deliverynozzle module 317 including fuel delivery nozzle 316, and the fuelreceptacle 22. Such a field of regard has a predetermined depth aft ofthe imaging system and in this example comprises sensing volume 359generally aft of the imaging system 350, which for example comprises aprismoidal volume or any other suitable shape, for example conical,frustoconical, cylindrical, spherical, part-spherical (e.g.hemispherical), parallelepiped (for example cubic) or any other regularor irregular shape. The sensing volume 359, i.e., the predetermineddepth of the FOR, extends beyond the position of the fuel deliverynozzle module 317 further than is required corresponding to theengagement enabling position, i.e., further than the maximum extensionof the aft section 314 when this is in its fully deployed position. Theimaging system 350 is operatively connected to a control computer system355, which can be integral with, connected to, or independent fromcontroller 390. In particular, such an object is the receiver aircraft20 and more particularly a part AP thereof including the fuel receptacle22 and/or another part of the receiver aircraft 20 (including a partthat does not include the fuel receptacle 22, but, when recognized, canenable estimation of the fuel receptacle 22 position and orientation),and the sensing volume 359 defines an outer envelope limit 358 in whichimage data of part AP can be processed, inter alia, by control computersystem 355. The control computer system 355 can then provide controlsignals, for example alignment commands, to the motion control system330, for example via controller 390, to control operation of the boomsystem 300, in particular the relative orientation of the boom fuellingunit 310 and the relative position of the nozzle 316 with respect to thereceiver aircraft 20, in particular with respect to the fuel receptacle22, so that the nozzle 316 can be controllably brought into selectiveengagement with the fuel receptacle 22 in a safe and effective manner

In this example, the imaging system 350 comprises one or more LightDetection And Ranging (LIDAR) units 351, which can utilize eye-safelaser. The imaging system 350 in this example is located on theunderside of the fuselage of the tanker aircraft 12′, but in alternativevariations of this example the imaging system 350 can be locatedelsewhere on the tanker aircraft 12′, for example the wings, elevators,etc., so long as the sensing volume 359 extends beyond the position ofthe nozzle 316 to include the nozzle module 317 and nozzle 316, and partAP when the part AP is in close proximity to the nozzle 316. Oneexemplary non-limiting alternative location is shown in the figure underreference numeral 350′.

In particular, and referring also to FIG. 31, the LIDAR unit 351 isconfigured for providing depth data and electromagnetic data (forexample electromagnetic intensity data) relating to any object withinthe sensing volume 359, in particular relating to one or more of thenozzle module 317, nozzle 316 and part AP.

In this example, the LIDAR unit 351 comprises a fiber laser unit 352configured for generating and radiating a laser beam B1 towardshorizontally rotated polygon 353, which in turn deflects the beam B1 toa mirror 354, which can be controllably moved in elevation. Thecontrolled combined motion of the mirror 354 and polygon 353 scans theoutgoing beam B1 in a two-dimensional pattern SC in sensing volume 359,along azimuth and elevation within sensing volume 359, for example withrespect to one or more planes BB orthogonal to a depth directionradiating from the LIDAR unit 351. Each time the outgoing beam B1impinges on an object within the sensing volume 359, a reflected beam B2returns along a path similar to that of the outgoing beam B1, deflectedby the mirror 354 and polygon 353, and detected by detector 356.

It is to be noted that in some cases, a single mirror which can berotated in two dimensions can be used instead of the mirror 354 andpolygon 353.

Control module 369 includes one or more of a fast Analog to DigitalConverter (ADC) card, Field Programmable Gate Array (FPGA), DigitalSignal Processor (DSP), memory and power supply for operation of theLIDAR unit 351.

Fast Analog to Digital Converter (ADC) card can be one having a typicalconversion speed of about 1.5 GHZ or more. The fiber laser unit 352 cangenerate a laser pulse having a very fast rising time therefore thereturning (i.e. the reflected) beam requires a very fast detector suchas an Avalanche Photo Diode. An Avalanche Photo Diode is a verysensitive Photo Diode which enables measuring the time of light with anaccuracy of typically about 10 centimeters. Such accuracy can be furtherincreased for example using the known functional time evolution of thelaser pulse. Using such algorithm, accuracies of few millimeters can beachieved.

The Field Programmable Gate Array (FPGA) can be used to enable therequired processing power for processing the data acquired by the LIDARunit 351.

The Digital Signal Processor (DSP) can be a real time processor that canbe configured to analyze the data acquired by the LIDAR unit 351 andprovide the electromagnetic data and the depth data. Such data can bestored in the memory and can be transferred (e.g. transmitted) forfurther computations in one or more additional/alternative computers.

The fiber laser unit 352 is a Fiber laser which can comprise an opticalfiber to which diode lasers (e.g. having a larger frequency than therequired laser radiation) are attached for providing the necessaryexcited medium (e.g. the light amplifying medium). In some cases, theinitiating laser diode at the required frequency is attached to thefiber and starts the laser operation. The laser beam is amplified in thefiber and an amplified beam goes out from the fiber to a collimatordevice to start the laser operation. A laser beam at 1.5 microns can beused, which is an eye safe light, since it cannot penetrate the corneaof the pilot and hence cannot focus on the retina and cause any damage.The laser beam can be typically composed of about one hundred thousandpulses per second. It is to be noted that the higher the number ofpulses is, the higher resolution can be achieved. In some cases, thepulse duration of the laser beam can be about 2 to 10 nanosecond width.The energy of the pulsed laser beam can be set according to the requiredsampling distance. In some cases, no more than one hundred meters areneeded, and in such cases the required energy is typically about five totwenty micro joules per pulse. The rise time of the laser beam can be ofabout few tenths of a nanosecond. This allows for accurate measurementof the time of light of the laser to the target. It is to be noted thatin some cases gas or solid state laser can be alternatively used.

At any particular position of the mirror 354 and polygon 353(corresponding to a two-dimensional position on plane BB, for example),the time interval between the outgoing beam B1 and the return beam B2being detected by the detector 356 provides a measure of the depth ofthe part of the object which reflected the beam, thereby providing thedepth data. In addition, the detector 356 also detects the intensity ofthe part of the object which reflected the beam to provide the intensitydata.

In alternative variations of this example, the LIDAR unit 351 can bereplaced with any other suitable imaging system 350 that provides depthdata and electromagnetic intensity data of objects within the sensingvolume 359 (including, but not limited to, Flash LADAR, 3D Flash LIDARCamera, etc.). In still further alternative variations of this example,the LIDAR unit 351 can be replaced with other suitable imaging systemssuch as stereoscopic cameras, conventional cameras, various radarsystems, etc.

In any case, the control computer system 355 comprises a memoryincluding geometrical data of the shape of at least part of the receiveraircraft 20, in particular part AP and or the fuel receptacle 22. Thecontrol computer system 355 is further configured for operating on thedepth data and the geometrical data to enable identification of a firstpart of the depth data that corresponds to the part AP and or the fuelreceptacle 22.

according to certain examples of examples of the presently disclosedsubject matter the data acquisition system 360 further includes boom tipmarker 340, comprised in the fuel delivery nozzle module 317 proximateto the nozzle 316. The boom tip marker 340 is at a fixed and knowngeometrical relationship with respect to the nozzle 316, independentlyof the relative motion between the boom system 300 and the tankeraircraft 12′, and is electromagnetically visible to the imaging system350, at least during operation thereof.

In this example, the boom tip marker 340 comprises a retro-reflectivesurface that reflects incident beams along the same path, and thusprovides a strong intensity reflection of the respective beam B2 whenilluminated by beam B1, as compared with the reflection intensityobtained from other surfaces of the boom fuelling unit 310, for example.Such a retro-reflective surface may be provided via a retro-reflectivematerial affixed to the fuel delivery nozzle module 317. Suchretro-reflective materials are well known in the art, and can includefor example retro-reflective tape or retro-reflective paint.

According to certain examples of examples of the presently disclosedsubject matter the data acquisition system 360 further includes fuelreceptacle marker 342, comprised on the receiver aircraft 20 in apre-determined location with respect to the fuel receptacle 22 thereof.The fuel receptacle marker 342 is at a fixed and known geometricalrelationship with respect to the fuel receptacle 22, and iselectromagnetically visible to the imaging system 350, at least duringoperation thereof.

In this example, the fuel receptacle marker 342 comprises aretro-reflective surface that reflects incident beams along the samepath, and thus provides a strong intensity reflection of the respectivebeam B2 when illuminated by beam B1, as compared with the reflectionintensity obtained from other surfaces of the receiver aircraft 20, forexample. Such a retro-reflective surface may be provided via aretro-reflective material affixed to a certain known location visible tothe imaging system 350 on the receiver aircraft 20. Suchretro-reflective materials are well known in the art, and can includefor example retro-reflective tape or retro-reflective paint.

It is to be noted that the data acquisition system 360 can include anyone of the boom tip marker 340 and the fuel receptacle marker 342, or acombination of both. Alternatively, in some cases, the data acquisitionsystem 360 can include none of the markers (in this case the naturalreflective properties of the surfaces can be used).

The control computer system 355 is further configured for operating onthe depth data and the electromagnetic intensity data to enableidentification of a second part of the depth data that corresponds tothe high intensity reflection originating from the boom tip marker 340,which in turn enables identification of the part of a third depth datathat corresponds to nozzle 316 since the relative spatial relationshipbetween the boom tip marker 340 and nozzle 316 is known.

Accordingly, when the aforesaid first part and second part (first partand third part) of the depth data is known, the control computer system355 can determine the relative disposition between the boom system 300,and in particular the nozzle 316, and the receiver aircraft 20, inparticular the fuel receptacle 22 thereof.

The tanker 12′ can be configured to provide the maneuvering instructionsfor enabling positioning of the receiver aircraft 20 within anengagement area, for example in a similar manner to that disclosedherein with reference to the examples of FIGS. 1 to 29, mutatismutandis, for example by utilizing a signaling system. Thus, suchsignaling system can be mounted, for example, on the tanker aircraft12′, at any location visible to the receiver aircraft 20 pilot. In somecases, the signaling system can provide the receiver aircraft 20 pilotwith maneuvering instructions on three axes: forward-backward,left-right and up-down, thus enabling it to maneuver the receiveraircraft 20 to the corresponding engagement area that allows forengagement between the fuel nozzle 316 and the fuel receptacle 22. Insome cases the signaling system can be a light directing system.Alternatively or additionally, the maneuvering instructions can beprovided to by using voice commands (e.g. by utilizing speakers, pilotheadset, etc.) or by any other means known per se. In some cases, amaneuvering instructions module can be configured to communicate themaneuvering instructions to an auto pilot system of the receiveraircraft 20, if such system exists, for causing the auto pilot system tomaneuver the receiver aircraft 20 accordingly.

The manner of operation of the imaging system 350 and control computersystem will be described in greater detail further herein.

In operation, the LIDAR unit 351 illuminates the sensing volume 359 andany object therein, in particular part AP of the receiver aircraft 20and thereafter acquire suitable image data corresponding thereto whichis sent to control computer system 355 for processing to provide theaforesaid control signals for controlling operation of the boom system300, in particular, to align the boom fuelling unit 310 to provide adesired relative position and orientation of the nozzle 316 with respectto the fuel receptacle 22, in particular the engagement enablingposition.

In alternative variations of this example and in other examples, theimaging system 350 can comprise any other suitable imaging system (forexample, but not limited to, systems providing 2D images and/orstereoscopic images and/or 3D images of (including reconstruction of 3Ddata corresponding to) the sensing volume 359, in particular but notlimited to images that are updated in real time, for example in the formof a video stream) that operate to provide suitable data to the controlcomputer system 355 to, in turn, enable selectively controlling the boomsystem 300 to provide autonomous and/or manual engagement of the nozzle316 to the fuel receptacle 22 of the receiver aircraft 20. For examplethe imaging system 350 can be similar to the imaging system disclosedherein with respect to the examples of FIGS. 1 to 29.

In alternative variations of this example, the fuelling unit 310 can bereplaced with any other conventional or non-conventional so-called“flying boom” systems.

In alternative variations of this example, the part AP can also comprisea retro-reflective surface to help identify the part of the depth datacorresponding to the part AP.

In alternative variations of this example, the boom tip marker 340and/or the fuel receptacle marker 342 can comprise an electromagneticsource, for example a light source of different wavelength from that ofthe illumination beam B1, and the illumination data received from therespective boom tip marker 340 and/or the respective fuel receptaclemarker 342 (via the imaging system 350 and/or a second imaging system).

In alternative variations of this example, the imaging system 350 can belocated in alternative locations on the refueling aircraft 12′ and/or onthe boom member 312, or on any other location.

There is now provided a description of certain examples of systems ofcontrolling in-flight refueling.

Reference is now made to FIG. 18, which is a block diagram schematicallyillustrating a system for controlling in-flight refueling, according tocertain examples of the presently disclosed subject matter. The system1805 comprises at least one processing unit 1801. The processing unit1801 can be a microprocessor, a microcontroller or any other computingdevice or module, including distributed and/or multiple processingunits, which are adapted to independently or cooperatively process datafor controlling relevant system 1805 components and for enablingoperations related to system 1805 components.

In some cases, the processing unit 1801 can be the control computersystem 155, or part thereof. In some cases, the processing unit can bethe controller 180. Alternatively, the processing unit 1801 can be aseparate component.

In some cases, the processing unit 1801 can be located on-board therefueling device 100, or on-board the receiver aircraft 20, or on-boardthe tanker aircraft 12. In some cases, more than one processing unit canbe used and the plurality of processors can be cooperatively operated.

In some cases, the system 1805 can be distributed between the refuelingdevice 100 and/or the receiver aircraft 20, and/or the tanker aircraft12 and/or any other location, including remote locations. Thecommunication between the various components of the system 1805 can berealized by any communication components, protocols and modules, and canbe wired or wireless.

The system 1805 further comprises a sensor control module 1810.According to some examples of the presently disclosed subject matter,the sensor control module 1810 can be configured to utilize at least onesensor 1890 (possibly according to instructions from the processing unit1801) as part of the operation of and control over the refuelingprocess.

The sensor control module 1810 can be operatively connected to at leastone sensor 1890 and can be configured to control the operation of thesensor 1890. The sensor 1890 can be a suitable data acquisition system,for example, any image acquisition means such as a camera (e.g. adigital still camera, a digital video camera, a Flash LADAR camera,etc.). Alternatively, the sensor 1890 can be a Light Detection AndRanging (LIDAR) unit (including one using an eye-safe laser), a radar(including a radar utilizing an eye-safe laser), a laser array(including a laser array that utilizes eye-safe lasers),electro-acoustic sensors, etc. An exemplary non-limiting LIDAR unit thatcan be used is described herein, inter alia with reference to FIGS.31-33. In some cases, sensor 1890 can be configured inter alia forproviding data of any object coming within a field of regard (FOR) aftof the refueling device 100 (and/or the tanker aircraft 12). In somecases, the sensor 1890 can be the imaging system 150 or imaging system350 detailed herein. In some cases, multiple sensors can be utilized,including, for example, a combination of the imaging system 150 and theimaging system 350, or multiple redundant sensors of same type. In somecases, such combination of sensors can enable determination of spatialdata also in cases when one of the imaging system 150 and the imagingsystem 350 does not provide the required data from some reason (e.g. dueto a malfunction or due to environmental conditions such as clouds,dazzling light, etc. or due to partial concealment of the FOR by othersystem components, such as concealment of receptacle by telescope, thatcan affect the sensors and/or the data received therefrom, or from anyother reason).

In some cases, imaging system 150 can be configured inter alia forproviding imaging data (including spatial disposition determinationenabling data such as data received from a LIDAR unit, etc.) of anyobject coming within a field of regard (FOR) aft of the refueling device100 (and/or the tanker aircraft 12). The sensor control module 1810 isconfigured to operate sensor 1890 (or multiple sensors, mutatismutandis) in order to acquire data that enables, inter alia, repeateddetermination of spatial data such as the spatial disposition of thereceiver aircraft 20 with respect to an engagement area related theretoand/or determination of the spatial dispositions of the refueling device100 with respect to an engagement enabling position, etc. as furtherdetailed herein, inter alia with respect to FIGS. 22 and 23.

The system 1805 can further comprise a maneuvering instructions module1820, a steering control module 1830, a safety module 1840, and anengagement/disengagement control module 1850.

Maneuvering instructions module 1820 can be configured to calculatemaneuvering instructions for enabling positioning of the receiveraircraft 20 within an engagement area related thereto, and for providingthe calculated maneuvering instructions to a pilot of the receiveraircraft 20, as further detailed, inter alia with respect to FIG. 20.

Steering control module 1830 can be configured, when anon-aircraft-fixed in-flight refueling system is used, to calculate andprovide steering commands (e.g. in six degrees of freedom) to therefueling device 100 for steering the refueling device 100 to anengagement enabling position or, when utilizing an aircraft-fixed flyingboom system, to calculate and provide alignment commands (e.g. in threedegrees of freedom) to the boom fueling unit 310 for aligning therefueling device 100 in an engagement enabling position, as furtherdetailed herein, inter alia with respect to FIG. 21. It is to be notedthat the steering commands (e.g. in six degrees of freedom) and thealignment commands (e.g. in three degrees of freedom) are also referredto as maneuvering commands interchangeably.

Safety module 1840 can be configured to monitor hazardous situations inthe refueling process, as further detailed herein, inter alia withrespect to FIG. 19. The hazardous situations can be defined by a set ofthresholds and/or parameters and respective safety conditions. Forexample, safety module 1840 can be configured to monitor that therefueling device 100 does not approach the receiver aircraft 20 (or viceversa) in an unsafe manner, and/or that the refueling device 100 doesnot approach the tanker aircraft 12 (or vice versa) in an unsafe manner,etc.

Engagement/disengagement control module 1850 can be configured toprovide an engagement command to the refueling device 100 for causingthe refueling device 100 to engage with the fuel receptacle 22 of thereceiver aircraft 20 for performing refueling, and to provide a commandto the refueling device 100 to disengage from the fuel receptacle 22 ofreceiver aircraft 20, as further detailed herein. According to examplesof the presently disclosed subject matter, engagement/disengagementcontrol module 1850 can be responsive to an indication that the receiveraircraft 20 is positioned in an engagement enabling position. Theengagement enabling position, in some cases, can depend on a spatialdisposition of the refueling device 100 with respect to the receiveraircraft 20, as further detailed herein.

The system 1805 can further comprise a configuration data repository1860 (hereinafter: “Configuration DR”) and a reference data repository1870 (hereinafter: “Reference DR”). Configuration DR 1860 comprises dataindicative of various predefined configurations that are used in therefueling process. According to examples of the presently disclosedsubject matter, the configuration DR 1860 can include configuration datarelated to an engagement area and an engagement enabling position.Further, by way of example, the configuration data related to theengagement area and the engagement enabling position can be used todetermine the engagement area and/or the engagement enabling position ina given scenario (and for a given set of parameters). Additional datawith respect to the configuration data will be provided herein, interalia with respect to FIGS. 22 and 23. Reference DR 1870 comprisesreference data to be used, inter alia, for determining (it is to benoted that in some cases such determination is made, for example,repeatedly) the receiver aircraft's 20 spatial disposition with respectto the engagement area related thereto and the refueling device's 100spatial disposition with respect to the engagement enabling position,etc. According to some examples, the reference data can be used incombination with dynamic data acquired by the sensor 1890 for enablingevaluation of the sensor's 1890 data. Further explanations regarding thereference data are provided herein, inter alia with respect to FIGS. 22and 23. It is to be noted that in some cases, Reference DR 1870 can alsobe used by the safety module 1840 for determining hazardous situations.

It is to be noted that according to some examples of the presentlydisclosed subject matter, some or all of the Configuration DR 1860, theReference DR 1870, the sensor control module 1810, the maneuveringinstructions module 1820, the steering control module 1830, the safetymodule 1840, and the engagement/disengagement control module 1850 can becombined and provided as a single system/module, or, by way of example,at least one of them can be realized in a form of two or moresystems/modules, each of which can in some cases be distributed overmore than one location.

The system can still further comprise an interface 1880 for enabling oneor more components of the system 1805 to operate in cooperation withauxiliary units, devices, systems or modules. For example, the interface1880 can implement various protocols, software languages, drive signals,etc. Further, by way of example, the interface 1880 can be used tooperate certain auxiliary units, devices, systems or modules on boardone or more of the refueling device 100, the receiver aircraft 20 or thetanker aircraft 12.

According to another aspect of the presently disclosed subject matter,there are provided methods for in-flight refueling of aircraft. Whilesuch methods can be applied to the systems and devices for in-flightrefueling of aircraft according to another aspect of the presentlydisclosed subject matter, and as disclosed herein, for example, themethods can also be applied to other suitable systems and devices forin-flight refueling of aircraft, mutatis mutandis.

According to the second aspect of the presently disclosed subjectmatter, there are at least three alternative operation modes forin-flight refueling of aircraft:

Operation Mode I—in which a refueling device is automatically (and insome cases autonomously) flown to engagement with the receiver aircraftfuel receptacle.

Operation Mode II—in which an operator in the tanker aircraft orelsewhere (via suitable communications link—for example satellite link,another aircraft including the receiver aircraft, ground control, and soon) controls flying of a refueling device while towed behind the tankeraircraft to engagement with the receiver aircraft fuel receptacle.

Operation Mode III—in which the refueling device is not flown orcontrolled per se, but instead attains a stable configuration with theboom member at the required inclination angle with respect to theforward direction, and the receiver aircraft maneuvers to a positionwhere it can engage the nozzle to the receiver aircraft fuel receptacle.

Examples of these operation modes will now be described in greaterdetail.

Operation Mode I

In this operation mode, once the tanker aircraft 12 and receiveraircraft 20 are in close proximity and flying in formation, with thereceiver aircraft 20 at a position behind the tanker aircraft 12, therefueling device 100 automatically (and in some cases, autonomously)flies into engagement with the fuel receptacle 22 of the receiveraircraft 20.

Turning to FIG. 19 there is provided a flowchart illustrating a sequenceof operations carried out for enabling performance of in-flightrefueling, according to certain examples of the presently disclosedsubject matter, in particular relating to the example of a system forcontrolling in-flight refueling, as illustrated in FIG. 18. The sequenceof operations begins with performance of an engagement sequence 1905,comprising 3 blocks: 1910, 1920 and 1930.

Turning at first to block 1910, in some cases, maneuvering instructionsmodule 1820 is configured to calculate and provide maneuveringinstructions for enabling positioning the receiver aircraft 20, and morespecifically a fuel receptacle 22 thereof, within an engagement arearelated to the receiver aircraft 20 (as in cases where more than onereceiver aircraft 20 exists, each receiver aircraft 20 can be associatedwith a different engagement area) (block 1910), as further detailedherein with respect to FIGS. 20 and 22. Inter alia, some examples ofmethods that can be used for providing the maneuvering instructions tothe pilot of the receiver aircraft 20 are also provided herein.

It is to be noted that such maneuvering instructions can be required insome cases, where the pilot of the receiver aircraft 20 has no line ofsight to the refueling device 100 or boom fuelling unit 310 during allor part of the refueling process, inter alia in light of the receiveraircraft 20 fuel receptacle 22 position. Thus, there can be a need toprovide the pilot of the receiver aircraft 20 with maneuveringinstructions, as further detailed herein.

As mentioned above, according to examples of the presently disclosedsubject matter, the refueling process can include providing maneuveringinstructions for positioning the receiver aircraft 20 within anengagement area related thereto. The engagement area is a virtual volumein which the refueling device 100 (when a non-aircraft-fixed in-flightrefueling system is used) or boom fuelling unit 310 (when utilizing anaircraft-fixed flying boom system) can be maneuvered in order to engagewith the fuel receptacle 22 of the receiver aircraft 20. According tosome examples of the presently disclosed subject matter, the engagementarea can be defined by various specifications that depend on severalparameters. According to one example, the parameters are associated withmaneuvering capabilities of the refueling device 100 (when anon-aircraft-fixed in-flight refueling system is used) or the boomfuelling unit 310 (when utilizing an aircraft-fixed flying boom system).Such maneuvering capabilities can be defined, for example, by the rangeand types of motion that can be achieved by utilizing the spatialcontrol system 160 and/or the force generating arrangement 190 of therefueling device 100 (when a non-aircraft-fixed in-flight refuelingsystem is used) or the mechanical connection 320 and/or the motioncontrol system 330 of the boom fuelling unit 310 (when utilizing anaircraft-fixed flying boom system), etc.

According to certain examples of the presently disclosed subject matter,the parameters defining the engagement area can further include, interalia, the length of the hose 52 (when a non-aircraft-fixed in-flightrefueling system is used), the length of the boom fuelling unit 310(when utilizing an aircraft-fixed flying boom system), the flight speed,the flight altitude, weather conditions, the fuel pressure within thehose 52 (when a non-aircraft-fixed in-flight refueling system is used),the location of the fuel receptacle 22 of the receiver aircraft 20, etc.In some cases, the engagement area can be substantially in the shape ofa cube, a sphere, or any other shape, including a non-regular shape,with a certain volume. The various engagement area specifications can bestored, for example, on configuration DR 1860. For example, theengagement area specifications can include a set of spatial dispositionsbetween the refueling device 100 and the receiver aircraft 20 or anyother volumetric specification. According to further examples of thepresently disclosed subject matter, the engagement area specificationscan be used in combination with reference data for enabling therefueling device 100, based on dynamic data acquired by the sensor 1890,to identify when the receiver aircraft 20 is within a position thatmeets the engagement area specification. In this case, correlations canbe computed between the data acquired by the sensor 1890 and thereference data, in order to determine if and when the receiver aircraft20 is within the engagement area, as further detailed herein, inter aliawith reference to FIG. 30-32.

Before moving on to describe FIG. 19, and for the purpose of providing avisual illustration of an exemplary engagement area, attention is drawnto FIG. 24, showing an illustration of one example of a receiveraircraft positioned outside a virtual engagement area, according tocertain examples of the presently disclosed subject matter. Theengagement area 2410 in the illustrated example is a virtualpre-determined volume, shaped substantially like a cube, in which therefueling device 100 (or, when utilizing an aircraft-fixed flying boomsystem—the boom fuelling unit 310) can navigate until engaging with thefuel receptacle 22 of the receiver aircraft 20, as detailed herein.Although in this example the virtual engagement area is shapedsubstantially like a cube, the virtual engagement area can have anyother shape with a certain volume. The virtual engagement area can bedefined by a set of parameters that correspond to a volumetric shape. Itcan be further appreciated that in the illustrated example, the receiveraircraft 20 is not positioned within the engagement area 2410. Theillustration of FIG. 24 is provided for clarity of explanation only andis by no means binding.

Returning to FIG. 19, in some cases, the engagement area specificationscan be defined using, inter alia, a parameter denoting a position of thecenter of such an engagement area, or any other point within theengagement area, and a set of offset vectors, collectively representinga volume. In some cases, the center (or any other point of reference) ofthe engagement area can be determined in accordance with one or more ofthe following parameters: the length of the hose 52 in a deployedposition (when a non-aircraft-fixed in-flight refueling system is used),the length of the boom fuelling unit 310 (when utilizing anaircraft-fixed flying boom system), a given pitch angle between the boomaxis 131 (when a non-aircraft-fixed in-flight refueling system is used)or the boom fuelling unit 310 (when utilizing an aircraft-fixed flyingboom system) and the forward direction A, a given yaw angle between theboom axis 131 (when a non-aircraft-fixed in-flight refueling system isused) or the boom fuelling unit 310 (when utilizing an aircraft-fixedflying boom system) and the forward direction A and a given fuelpressure within the hose 52 (when a non-aircraft-fixed in-flightrefueling system is used), etc. One or more of the parameters which areused to determine the center (or any other point of reference) of theengagement area can vary during flight and/or during the engagementsequence 1905 and the system 1805 can measure the relevant parametersdynamically for determining the center (or any other point of reference)of the engagement area.

In some cases (e.g. when a non-aircraft-fixed in-flight refueling systemis used), the point of reference for the engagement area can bepositioned in a position from which utilization of the force generatingarrangement 190 enables the nozzle 135 to engage with the fuelreceptacle 22 of the receiver aircraft 20 and the engagement area isdefined with reference to this point. In other cases (e.g. whenutilizing an aircraft-fixed flying boom system), the point of referencefor the engagement area can be positioned in a position which enablesthe nozzle 316 to engage with the fuel receptacle 22 of the receiveraircraft 20 (e.g. by extending the telescoping aft section 314 thusapplying force on the fuel receptacle 22 due to reaction force on theother side of the boom fuelling unit 310, at the mechanical connection320) and the engagement area is defined with reference to this point.

In some examples, this point of reference is defined in the system as anengagement enabling position, and can also be used by anengagement/disengagement control module 1850, for controlling engagementand of the nozzle 135 (or nozzle 316) with the fuel receptacle 22 of thereceiver aircraft 20. It will be appreciated that this point can alsodepend, inter alia, on the parameters described herein, and in somecases, is dynamically calculated according to the relevant parametersduring the engagement sequence 1905.

According to some examples of the presently disclosed subject matter,e.g. when a non-aircraft-fixed in-flight refueling system is used, theengagement enabling position can be characterized by the boom member 130being in a predetermined maximal spaced and spatial relationship withrespect to the fuel receptacle 22 of the receiver aircraft 20. Accordingto some examples of the presently disclosed subject matter, e.g. whenutilizing an aircraft-fixed flying boom system, the engagement enablingposition can be characterized by the boom fuelling unit 310 (or nozzle316 thereof) being in a predetermined maximal spaced and spatialrelationship with respect to the fuel receptacle 22 of the receiveraircraft 20.

Throughout the description and the claims, reference is madeinterchangeably to the terms spatial relationship and spatialdisposition. The terms spatial relationship and spatial disposition orthe like can relate to spatial distances, spatial angles (includingorientations), or any other spatial reference that is used forcharacterizing a spatial relationship between two objects, e.g. betweenany two of the following: the tanker aircraft 12, the receiver aircraft20 (and a fuel receptacle 22 thereof), the refueling device 100 and theboom fuelling unit 310. In some cases the spatial relationship caninclude aligning the boom axis 131 of the boom member 130 (e.g. when anon-aircraft-fixed in-flight refueling system is used) or the boom axis311 of the boom fuelling unit 310 (e.g. when utilizing an aircraft-fixedflying boom system), in an engagement enabling orientation.

In some cases, when a non-aircraft-fixed in-flight refueling system isused, the maximal spaced relationship between the boom member 130 of therefueling device 100 and the fuel receptacle 22 of the receiver aircraft20 at the engagement enabling position can depend on various parameters,such as: the hose 52 length and flexibility, the flight speed, theflight altitude, the characteristics of the force generating arrangement190, etc., and in such cases, the maximal space can be calculated asnecessary, inter alia dynamically during the refueling process, based oncurrent values of the respective parameters. For example, it can beappreciated that the less flexible the hose 52, the maximal spacebetween the boom member 130 of the refueling device 100 and the fuelreceptacle 22 of the receiver aircraft 20 at the engagement enablingposition is reduced. In some cases, the maximal space between the boommember 130 of the refueling device 100 and the fuel receptacle 22 of thereceiver aircraft 20 at the engagement enabling position can be definedby the movement range of the boom member 130 in the direction of thefuel receptacle 22 of the receiver aircraft 20.

In some cases, when utilizing an aircraft-fixed flying boom system, themaximal spaced relationship between the boom member 312 of the boomfuelling unit 310 and the fuel receptacle 22 of the receiver aircraft 20at the engagement enabling position can also depend on variousparameters, such as: the flight speed, the flight altitude, etc., and insuch cases, the maximal space can be calculated as necessary, inter aliadynamically during the refueling process, based on current values of therespective parameters. In some cases, the maximal space between the boommember 312 of the boom fuelling unit 310 and the fuel receptacle 22 ofthe receiver aircraft 20 at the engagement enabling position can bedefined by the extension range of the telescoping aft section 314 in thedirection of the fuel receptacle 22 of the receiver aircraft 20.

In some cases, the spatial relationship between the boom member 130 ofthe refueling device 100 (e.g. when a non-aircraft-fixed in-flightrefueling system is used), or the boom fuelling unit 310 (e.g. whenutilizing an aircraft-fixed flying boom system), and the fuel receptacle22 of the receiver aircraft 20 at the engagement enabling position canalso depend on various parameters, such as the characteristics of thefuel receptacle 22 of the receiver aircraft 20, etc. According toexamples of the presently disclosed subject matter the spatialrelationship with which the engagement enabling position is associatedcan also include an angle parameter. In this regard, it can beappreciated that in case the fuel receptacle 22 of the receiver aircraft20 has an entrance angle, the boom axis 131 of the boom member 130 (e.g.when a non-aircraft-fixed in-flight refueling system is used), or theboom axis 311 of the boom fuelling unit 310 (e.g. when utilizing anaircraft-fixed flying boom system), should be in a spatial dispositionthat enables the nozzle (nozzle 135 or nozzle 316) to engage therewith(e.g. the boom axis 131 or boom axis 311 needs to be aligned with a fuelreceptacle 22 of the receiver aircraft 20).

It has been explained herein that when a non-aircraft-fixed in-flightrefueling system is used spatial control system 160 can, in accordancewith certain examples, be configured for selectively and controllablyproviding a non-zero angular disposition, angle θ, between the boom axis131 and the forward direction A, that enables this angle θ to beselectively maintained between the boom axis 131 and the forwarddirection A at least for a part of the time when the refueling device100 is being towed by the tanker aircraft 12 via hose 52, and inparticular during the engagement operation of the fuel device 100 to thereceiver aircraft 20 and during refueling thereof. It is to be notedthat such angle θ can be predetermined. In some cases the angle θ can bestored in the configuration DR 1860.

It is to be noted that when utilizing an aircraft-fixed flying boomsystem, a mechanical connection 320 and/or a motion control system 330can be utilized for selectively and controllably providing a non-zeroangular disposition, angle θ, between the boom axis 311 and the receiveraircraft (e.g., between the boom axis 311 and. forward direction, A whenthe receiver aircraft is also aligned with forward direction A) andselectively maintain this angle θ at least for a part of the time duringthe engagement operation of the boom fuelling unit 310 to the receiveraircraft 20 and during refueling thereof. It is to be noted that suchangle θ can be predetermined, and can lie within a range of angles inwhich such engagement between the boom fuelling unit 310 to the receiveraircraft 20. In some cases the angle θ can be stored in theconfiguration DR 1860.

In some examples, it is to be noted that the engagement enablingposition is not necessarily a specific x, y, z coordinate, as, undercertain conditions, the exact coordinates of the point of reference forthe engagement area can vary, or some tolerance can be accepted (forexample using tolerance ranges). In addition, there can be more than oneengagement enabling position that meets the conditions detailed herein,each of which is an engagement enabling position.

Before moving on to describe FIG. 19, and for the purpose of providing avisual illustration of an exemplary engagement enabling position,attention is drawn to FIG. 26 and FIG. 27. Reverting to FIG. 26, thereis shown an illustration of an example of a refueling device not in anengagement enabling position, according to certain examples of thepresently disclosed subject matter. It can be appreciated that thereceiver aircraft 20, and more particularly a fuel receptacle 22thereof, is positioned within the engagement area 2410, however, therefueling device 100 is not positioned in an engagement enablingposition. In this example, as illustrated in FIG. 26, it can beappreciated that the refueling device 100 is not aligned with the fuelreceptacle 22 of the receiver aircraft 100. The illustration of FIG. 26is provided for clarity of explanation only and is by no means binding.Reverting to FIG. 27, there is shown an illustration of an example of arefueling device positioned in an engagement enabling position,according to certain examples of the presently disclosed subject matter.It can be appreciated that the refueling device 100 is positioned in anengagement enabling position that can enable engagement with the fuelreceptacle 22 of the receiver aircraft 100. The illustration of FIG. 27is provided for clarity of explanation only and is by no means binding.

It is to be noted that a refueling device 100 is shown in FIGS. 24-27for illustration purposes only and other refueling systems can also beused, including, but not limited to, a boom fuelling unit 310 as furtherdetailed herein.

Returning to FIG. 19, in some cases, maneuvering instructions module1820 can be configured to provide the maneuvering instructions forenabling positioning of the receiver aircraft 20 within an engagementarea, for example by utilizing a signaling system. Such signaling systemcan be mounted, for example, on the tanker aircraft 12, at any locationvisible to the receiver aircraft 20 pilot. In some cases, the signalingsystem can provide the receiver aircraft 20 pilot with maneuveringinstructions on three axes: forward-backward, left-right and up-down,thus enabling it to maneuver the receiver aircraft 20 to the engagementarea 2410. In some cases the signaling system can be a light directingsystem. Alternatively or additionally, the maneuvering instructions canbe provided to by using voice commands (e.g. by utilizing speakers,pilot headset, etc.) or by any other means known per se. In some cases,maneuvering instructions module 1820 can be configured to communicatethe maneuvering instructions to an auto pilot system of the receiveraircraft 20, if such system exists, for causing the auto pilot system tomaneuver the receiver aircraft 20 accordingly.

Before moving on to describe FIG. 19, and for the purpose of providing avisual illustration of an exemplary engagement area, attention is drawnto FIG. 25, showing an illustration of an example of a receiver aircraftpositioned inside a virtual engagement area, according to certainexamples of the presently disclosed subject matter. It can be noted thatthe receiver aircraft 20, and more particularly the fuel receptacle 22thereof, are positioned within the engagement area 2410. Also in thisillustration the engagement area 2410 is a virtual pre-determinedvolume, shaped substantially like a cube, in which, when anon-aircraft-fixed in-flight refueling system is used, the refuelingdevice 100 can navigate until arriving at an engagement enablingposition (in which the boom member 130 when a non-aircraft-fixedin-flight refueling system is used or the boom fuelling unit 310 (ornozzle 316 thereof) when utilizing an aircraft-fixed flying boom system,is in a predetermined maximal spaced and spatial relationship withrespect to the fuel receptacle 22 of the receiver aircraft 20) andengaging with the fuel receptacle 22 of the receiver aircraft 20, asdetailed herein.

Although also in this example the virtual engagement area is shapedsubstantially like a cube, the virtual engagement area can have anyother shape with a certain volume. It can be noted that the illustrationfurther illustrates an example of a signaling system 2420 mounted ontanker aircraft 12. It can be appreciated that such a signaling systemcan be used by maneuvering instructions module 1820 for providingmaneuvering instructions to the pilot of the receiver aircraft 20. It isto be noted that alternative and/or additional signaling systems can beused. The illustration of FIG. 25 is provided for clarity of explanationonly and is by no means binding.

Bearing all this in mind, and returning to FIG. 19, it is to be notedthat block 1910 can be performed repeatedly (e.g. every pre-determinedperiod) or continuously, at least until the nozzle 135 or nozzle 316 isengaged with the fuel receptacle 22 of the receiver aircraft 20, asfurther detailed herein. Thus, while the receiver aircraft 20 is notpositioned within the engagement area, maneuvering instructions module1820 provides the pilot of the receiver aircraft 20 (and, in some cases,an auto pilot system that controls the maneuvering of the receiveraircraft 20) with maneuvering instructions for positioning the receiveraircraft 20 within an engagement area.

Although the process above (referring to block 1910) was described withrespect to maneuvering of the receiver aircraft 20, it is to be notedthat in some cases, in addition or as an alternative to maneuvering ofthe receiver aircraft 20 for approaching the refueling device 100 or theboom fuelling unit 310, the tanker aircraft 12 can approach the receiveraircraft 20, thus bringing the refueling device 100 or the boom fuellingunit 310 in the direction of the receiver aircraft 20. In such cases,the maneuvering instructions can be additionally or alternativelyprovided to the pilot of the tanker aircraft 12 mutatis mutandis.

It is to be further noted that the process relating to block 1910 can insome cases be an independent process, and in other cases it can beperformed as part of a sequence of processes, such as engagementsequence 1905.

Turning now to block 1920 in FIG. 19, in some cases, when anon-aircraft-fixed in-flight refueling system is used, once anengagement area specification condition is met (e.g. it is determinedthat the receiver aircraft 20 is positioned within the engagement area),steering control module 1830 can be configured to provide commands forcausing the steering of the refueling device 100 to an engagementenabling position, in which the boom member 130 is in a predeterminedmaximal spaced and spatial relationship with respect to the fuelreceptacle 22 of the receiver aircraft 20 (block 1920), as furtherdetailed herein, inter alia with respect to FIGS. 21 and 23.

In some cases, the steering commands module 1830 can be operativelyconnected to the spatial control system 160 and/or to the forcegenerating arrangement 190 of the refueling device 100. In such cases,the steering commands module 1830 can provide steering commands forcontrolling the spatial control system 160 and/or to the forcegenerating arrangement 190 and thus enabling steering the refuelingdevice 100 to an engagement enabling position, in which the boom member130 is in a predetermined maximal spaced and spatial relationship withrespect to the fuel receptacle 22 of the receiver aircraft 20.

In some cases, the steering commands can be based, inter alia, oncharacteristics of the spatial control system 160. Such characteristicscan be, for example, operation parameters of reaction control thrustersassociated with the refueling device and capable of steering therefueling device 100 and/or operation parameters of aero-dynamic controlsurfaces of the refueling device 100.

In some cases, based on the steering commands from the steering commandsmodule 1830, the refueling device 100 can be adapted to steerautomatically. In particular, in some cases, using the commands,autonomous steering of the refueling device 100 can be achieved (e.g.when all the necessary components are fitted within the refueling device100).

Thus, in accordance with some examples of the presently disclosedsubject matter, there can be provided a refueling device 100 which canbring itself automatically, and in some cases (when all the necessarycomponents are fitted within the refueling device 100) autonomously,into fluid communication with the fuel receptacle 22 of the receiveraircraft 20. In further examples, there can be provided a refuelingdevice which can automatically, and in some cases (when all thenecessary components are fitted within the refueling device 100)autonomously, align its boom axis 131 with a fuel receptacle 22 of thereceiver aircraft 20, and move the boom member 130 in a predeterminedtrajectory towards the receiver aircraft 20 and thus enable therefueling device 100 to automatically bring itself into engagement withthe fuel receptacle 22 of the receiver aircraft 20.

It is to be noted that block 1920 can be performed repeatedly (e.g.every pre-determined period) or continuously. For example, block 1920can be performed until engagement of the nozzle 135 to the fuelreceptacle 22 of the receiver aircraft 20, as further detailed herein,and in some cases even after such engagement. While the refueling device100 is not positioned within an engagement enabling position, steeringcontrol module 1830 provides the refueling device 100 with steeringcommands for maneuvering the refueling device 100 to the engagementenabling position, in which the boom member 130 is in a predeterminedmaximal spaced and spatial relationship with respect to the fuelreceptacle 22 of the receiver aircraft 20.

According to some examples of the examples of the presently disclosedsubject matter, when utilizing an aircraft-fixed flying boom system,once an engagement area specification condition is met (e.g. it isdetermined that the receiver aircraft 20 is positioned within theengagement area), steering control module 1830 can be configured toprovide commands for aligning the boom fuelling unit 310 in anengagement enabling position, in which the boom member 311 is in apredetermined maximal spaced and spatial relationship with respect tothe fuel receptacle 22 of the receiver aircraft 20.

In some cases, the steering commands module 1830 can be operativelyconnected to the mechanical connection 320 and/or a motion controlsystem 330 and/or to the telescoping aft section 314 of the boomfuelling unit 310. In such cases, the steering commands module 1830 canprovide alignment commands for controlling a mechanical connection 320and/or a motion control system 330 and/or to a telescoping aft section314 of the boom fuelling unit 310 and thus enabling aligning therefueling device 100 at an engagement enabling position, in which theboom fuelling unit 310 is in a predetermined maximal spaced and spatialrelationship with respect to the fuel receptacle 22 of the receiveraircraft 20. It is to be noted that the alignment commands can result inmotion of the aircraft-fixed flying boom system in three degrees offreedom (e.g. pitch, yaw and translation).

In some cases, the alignment commands can be based, inter alia, oncharacteristics of the mechanical connection 320 and/or the motioncontrol system 330 and/or the telescoping aft section 314 of the boomfuelling unit 310.

In some cases, based on the alignment commands from the steeringcommands module 1830, the boom fuelling unit 310 can be adapted to alignitself automatically. In particular, in some cases, using the commands,autonomous aligning of the boom fuelling unit 310 can be achieved (e.g.when all the necessary components are fitted within the boom fuellingunit 310).

Thus, in accordance with some examples of the presently disclosedsubject matter, there can be provided a boom fuelling unit 310 which canbring itself automatically, and in some cases (when all the necessarycomponents are fitted within the boom fuelling unit 310) autonomously,into fluid communication with the fuel receptacle 22 of the receiveraircraft 20. In further examples, there can be provided a boom fuellingunit 310 which can automatically, and in some cases (when all thenecessary components are fitted within the boom fuelling unit 310)autonomously, align itself with a fuel receptacle 22 of the receiveraircraft 20, and move itself in a predetermined trajectory towards thereceiver aircraft 20 and thus enable the boom fuelling unit 310 toautomatically bring itself into engagement with the fuel receptacle 22of the receiver aircraft 20.

It is to be noted that block 1920 can be performed repeatedly (e.g.every pre-determined period) or continuously. For example, block 1920can be performed until engagement of the boom fuelling unit 310 to thefuel receptacle 22 of the receiver aircraft 20, as further detailedherein, and in some cases even after such engagement. While the boomfuelling unit 310 is not positioned within an engagement enablingposition, steering control module 1830 provides the boom fuelling unit310 with alignment commands for maneuvering the boom fuelling unit 310to the engagement enabling position, in which it is in a predeterminedmaximal spaced and spatial relationship with respect to the fuelreceptacle 22 of the receiver aircraft 20.

It is to be further noted that the process relating to block 1920 can insome cases be an independent process, and in other cases it can beperformed as part of a sequence of processes, such as engagementsequence 1905.

Attention is now drawn to block 1930 in FIG. 19. In some cases, when anon-aircraft-fixed in-flight refueling system is used, once the receiveraircraft 20 is positioned within the engagement area and the refuelingdevice 100 is positioned in an engagement enabling position (in whichthe boom member 130 is in a predetermined maximal spaced and spatialrelationship with respect to the fuel receptacle 22 of the receiveraircraft 20), the engagement/disengagement control module 1850 can beconfigured to provide the refueling device 100 with an engagementcommand for causing the refueling device 100 to engage to the fuelreceptacle 22 of the receiver aircraft 20 for enabling refueling of thereceiver aircraft 20 (block 1930). It is to be noted that at theengagement enabling position the nozzle 135 is properly aligned with thefuel receptacle 22 (the boom member 130 and boom axis 131 being at thedesign angle θ_(des) to the forward direction A) and sufficiently closethereto, i.e., at a predetermined spacing from the receiver aircraft,said boom axis being aligned in an engagement enabling orientation atsaid spaced position.

In some cases, the engagement command can cause activation of the forcegenerating arrangement 190, e.g., by deploying the air brakes 195, 196,thus generating a force along boom axis 131 that effectively pushes thenozzle 135 into engagement with the fuel receptacle 22 of the receiveraircraft 20. Such force can cause the boom member 130 to move in apredetermined trajectory towards the receiver aircraft 20 for enablingengagement between the nozzle 135 and the fuel receptacle 22 of thereceiver aircraft 20 (e.g. for enabling fuel communicationtherebetween). In some cases, prior to deploying the air brakes 195,196, the boom member 130 can be extended, for example until reaching apre-determined space from the fuel receptacle 22 of the receiveraircraft 20. In some cases, the engagement command can cause extensionof the boom member 130 until connection with the fuel receptacle 22 ofthe receiver aircraft 20, with no use of any air brakes mechanism. Inother words, once the refueling device 100 is at the aforesaidengagement enabling orientation and spaced position, the boom member issubsequently moved along said boom axis towards the receiver aircraftfor enabling fuel communication therebetween. Movement of the boommember can be effected in one of two ways, or combination thereof: therefueling device 100 remains in the spaced position, and the boom member130 is extended telescopically; the boom member 130 can be in theretracted or extended position, and the refueling device 100 is bodilymoved towards the receiver aircraft for enabling fuel communicationtherebetween.

In accordance with some examples of the presently disclosed subjectmatter, there can be provided a refueling device 100 which can bringitself automatically, and in some cases (when all the necessarycomponents are fitted within the refueling device 100) autonomously,into fluid communication with the fuel receptacle 22 of the receiveraircraft 20. In further examples, there can be provided a refuelingdevice 100 which can automatically, and in some cases (when all thenecessary components are fitted within the refueling device 100)autonomously, engage the nozzle 135 with the fuel receptacle 22 of thereceiver aircraft 20.

In some cases, prior to providing the refueling device 100 with anengagement command, maneuvering instructions module 1820 can beconfigured to cause a signaling system to provide the pilot of thereceiver aircraft 20 with a notification indicating that the refuelingdevice 100 is about to engage to the fuel receptacle 22, thus requiringthe pilot of the receiver aircraft 20 to stabilize it.

According to some examples of the examples of the presently disclosedsubject matter, when utilizing an aircraft-fixed flying boom system,once the receiver aircraft 20 is positioned within the engagement areaand the boom fuelling unit 310 is positioned in an engagement enablingposition (in which it is in a predetermined maximal spaced and spatialrelationship with respect to the fuel receptacle 22 of the receiveraircraft 20), the engagement/disengagement control module 1850 can beconfigured to provide the boom fuelling unit 310 with an engagementcommand for causing the boom fuelling unit 310 to engage to the fuelreceptacle 22 of the receiver aircraft 20 for enabling refueling of thereceiver aircraft 20. It is to be noted that at the engagement enablingposition the boom member 312 is aligned such that the nozzle tip issufficiently close to the fuel receptacle 22 of the receiver aircraft20, i.e., at a predetermined spacing from the fuel receptacle 22 of thereceiver aircraft 20, said boom axis 311 being aligned in an engagementenabling orientation at said spaced position.

In some cases, the engagement command can cause extension of thetelescoping aft section 314 thus applying force on the fuel receptacle22 due to reaction force on the other side of the boom fuelling unit310, at the mechanical connection 320.

In accordance with some examples of the presently disclosed subjectmatter, there can be provided a boom fuelling unit 310 which can bringitself automatically, and in some cases (when all the necessarycomponents are fitted within the boom fuelling unit 310) autonomously,into fluid communication with the fuel receptacle 22 of the receiveraircraft 20. In further examples, there can be provided a boom fuellingunit 310 which can automatically, and in some cases (when all thenecessary components are fitted within the boom fuelling unit 310)autonomously, engage the nozzle 316 with the fuel receptacle 22 of thereceiver aircraft 20.

In some cases, prior to providing the boom fuelling unit 310 with anengagement command, maneuvering instructions module 1820 can beconfigured to cause a signaling system to provide the pilot of thereceiver aircraft 20 with a notification indicating that the boomfuelling unit 310 is about to engage to the fuel receptacle 22, thusrequiring the pilot of the receiver aircraft 20 to stabilize it.

It is to be further noted that the process relating to block 1930 can insome cases be an independent process, and in other cases it can beperformed as part of a sequence of processes, such as engagementsequence 1905.

Attention is now drawn to Block 1940 in FIG. 19. In some cases,following engagement sequence 1905, the system 1805 can be configured toprovide a command to the refueling device 100 to perform refueling ofthe receiver aircraft 20 by pumping fuel to the receiver aircraft 20from the tanker aircraft 12 (block 1940). In some cases, when anon-aircraft-fixed in-flight refueling system is used, at any timefollowing engagement sequence 1905, the system 1805 can be furtherconfigured to deactivate the force generating arrangement 190, e.g. byretracting the air brakes 195, 196. In one example, the command todeactivate the force generating arrangement 190 and the refuelingcommand can be issued by the engagement/disengagement module 1850.Further by way of example, engagement/disengagement module 1850 can beconfigured to provide a deactivation command when an indication isreceived that the refueling device 100 is engaged with the receiveraircraft 20. Further by way of example, the refueling command can beissued for example when an engagement indication is issued.

Attention is now drawn to Block 1950 in FIG. 19. theengagement/disengagement control module 1850 can be further configuredto provide the refueling device 100 (when a non-aircraft-fixed in-flightrefueling system is used) or the boom fuelling unit 310 (when utilizingan aircraft-fixed flying boom system) with a disengagement command forcausing it to disengage from the fuel receptacle 22 of the receiveraircraft 20 in response to receiving an indication that the fuel levelin the fuel tank of the receiver aircraft 20 reached a desired level orwhen an indication of a hazard is issued (block 1950).

In some cases, prior to providing the refueling device 100 (when anon-aircraft-fixed in-flight refueling system is used) or the boomfuelling unit 310 (when utilizing an aircraft-fixed flying boom system)with a disengagement command, maneuvering instructions module 1820 canbe configured to cause the signaling system to provide the pilot of thereceiver aircraft 20 with a notification indicating that the refuelingis done, and in some cases instruct the pilot of the receiver aircraft20 to perform a maneuver in order to fly away from the refueling device100.

It is to be noted that throughout the refueling process, safety module1840 can monitor certain parameters, for example parameters that relateto the spatial dispositions between any two or more of the following:the receiver aircraft 20, the refueling device 100 (when anon-aircraft-fixed in-flight refueling system is used) the boom fuellingunit 310 (when utilizing an aircraft-fixed flying boom system) and thetanker aircraft 12, as well as other parameters including the angles,etc., possibly in comparison to predefined reference thresholds orparameters or ranges, to identify possible hazardous situations. Suchhazardous situations can include, inter alia, a dangerous approach ofthe receiver aircraft 20 to the refueling device 100 or to the tankeraircraft 12, a dangerous movement of the receiver aircraft 20, and/orthe refueling device 100 (when a non-aircraft-fixed in-flight refuelingsystem is used) and/or the boom fuelling unit 310 (when utilizing anaircraft-fixed flying boom system) and/or the tanker aircraft 12,including such movement when the refueling device 100 or the boomfuelling unit 310 is engaged to the receiver aircraft 20, etc. It is tobe noted that such hazardous situations can be caused for example due toa human error, environmental conditions (weather, wind, etc.), as wellas other causes. It is to be further noted that for monitoring suchhazardous situations, safety module 1840 can be configured to utilize,inter alia, sensor control module 1810 for sensing the spatialdispositions of the receiver aircraft 20, and/or the refueling device100 and/or the boom fuelling unit 310 and/or the tanker aircraft 12.

In some cases, when safety module 1840 identifies a hazardous situation(e.g. a safety condition is met or, in some cases, is not met), it canbe configured, inter alia, to instruct steering control module 1830 toprovide steering instructions for causing the refueling device 100 tosteer away from the receiver aircraft 20 (when a non-aircraft-fixedin-flight refueling system is used) or to provide commands formaneuvering the boom fuelling unit 310 away from the receiver aircraft20, and/or to provide an indication to the pilot of the receiveraircraft 20 that a hazardous situation has been identified, thusenabling the pilot to maneuver the receiver aircraft 20 away fromdanger, etc. It is to be noted that in case the hazardous situation isidentified after the refueling device 100 (when a non-aircraft-fixedin-flight refueling system is used) or the boom fuelling unit 310 (whenutilizing an aircraft-fixed flying boom system) engaged with thereceiver aircraft 20, safety module 1840 can be further configured toinstruct engagement/disengagement module 1850 to cause the refuelingdevice 100 or the boom fuelling unit 310 to disengage from the receiveraircraft 20 prior to performing the maneuvering as detailed herein.

It is to be noted that in some cases, when the receiver aircraft 20 ispositioned within the engagement area, or at an earlier stage, therefueling device 100 (when a non-aircraft-fixed in-flight refuelingsystem is used) and/or the boom fuelling unit 310 (when utilizing anaircraft-fixed flying boom system) can be deployed to an initial trailposition. Such initial trail position can be defined in terms of aspatial disposition with respect to the tanker aircraft 12 and can becharacterized, inter alia, by one or more of the following:

-   -   When a non-aircraft-fixed in-flight refueling system is used—a        required deployment length of the hose 52 (that in some cases        can depend, inter alia, on the flight speed, the flight        altitude, the receiver aircraft 20 type, the engagement area        specification, etc., whereas in other cases it can be for        example pre-determined) or, when utilizing an aircraft-fixed        flying boom system, the extension length of the telescoping aft        section 314;    -   A required pitch angle between the boom axis 131 or boom axis        311 and the forward direction A is maintained;    -   A required yaw angle between the boom axis 131 or boom axis 311        and the forward direction A is maintained.

In some cases, the steering control module 1830 can be configured tomonitor the spatial disposition of the refueling device 100 and/or theboom fuelling unit 310 with respect to the tanker aircraft 12 andvalidate that the refueling device 100 and/or the boom fuelling unit 310is positioned in the initial trail position with respect to the tankeraircraft 12. For that purpose, steering control module 1830 can utilize,for example, sensor control module 1810 for repeatedly, and in somecases in real time (for example in the form of a video stream) acquiringan image of the area in which the refueling device 100 and/or the boomfuelling unit 310 is expected to be positioned when in the initial trailposition. The image can be acquired by a sensor 1890 that can bemounted, for example, on the tanker aircraft 12 in a position thatenables it to acquire images of the area in which the refueling device100 and/or the boom fuelling unit 310 is expected to be positioned whenin the initial trail position. Such sensor position can be, for example,on the tanker aircraft 12 wing, elevators, tail, on the underside of thefuselage, etc. Utilization of such an image can enable determination ofthe refueling device's 100 and/or the boom fuelling unit 310 spatialdisposition with respect to the tanker aircraft 12 (it is to be notedthat in some cases such determination is made, for example, repeatedly).For example, the acquired image can be compared with a pre-stored image(e.g. stored on reference data repository 1870) of the refueling device100 and/or the boom fuelling unit 310, illustrating a desired spatialdisposition with respect to the tanker aircraft 12, thus enablingdetermination of the relative spatial disposition of the refuelingdevice 100 and/or the boom fuelling unit 310 with respect to the tankeraircraft 12 (it is to be noted that in some cases such determination ismade, for example, repeatedly). Such desired spatial disposition can, insome cases, depend on various factors, such as, inter alia, the flightspeed, the flight altitude, the refueling device 100 weight, etc. It canbe appreciated that pre-stored images of different spatial dispositionsof the refueling device 100 and/or the boom fuelling unit 310 withrespect to the tanker aircraft 12 can be stored in reference DR 1870 anda set of parameters, inter alia, flight speed, flight altitude,refueling device 100 weight, etc., can be specified in association withone or more of the pre-stored images.

According to examples of the presently disclosed subject matter, for agiven set of parameters, steering control module 1830 can determinewhich image is to be used as a reference image. For example, thesteering control module 1830 can receive a set of measurements which arecorrelated with the parameters associated with the images and cancompare the current measurements to the various sets of parameters andidentify which set is, for example, most closely correlated with themeasurements and the steering control module 1830 can select the imagewith which the parameters are associated as the reference image.Following the selection of the reference image, the steering controlmodule 1830 can repeatedly (e.g. every pre-determined period), orcontinuously, compare images obtained by the sensor 1890 during therefueling process to the selected reference image, and calculate thespatial disposition of the refueling device 100 with respect to theinitial trail position.

In some cases, 3-D models can be used instead of images. According tofurther examples, the reference DR 1870 can store one or more generic3-D models (e.g. one for each type of aircraft), and as part ofdetermining the spatial disposition of the refueling device 100 and/orthe boom fuelling unit 310 with respect to the tanker aircraft 12, anappropriate 3-D model can be selected (for example according to the typeof the receiver aircraft 20) and the 3-D model can be adapted usingcurrent measurements (e.g. obtained by the sensor 1890) and respectiveparameters of the 3-D model.

According to other examples of the presently disclosed subject matter,steering control module 1830 can search among the different pre storedreference images for an image which most closely correlates with acurrent image and can determine the spatial disposition using thepre-stored parameters associated with the selected image.

In some cases, the sensor 1890 can be a LIDAR unit 351. In such cases,the sensor can acquire the images as further detailed herein, inter aliawith reference to FIGS. 30-32. The images obtained by the LIDAR unit 351can comprise both depth data and electromagnetic data within the sensingvolume 359. In such cases, the depth and electromagnetic data can becompared with look up tables comprising reference depth data andreference electromagnetic data relating to reference spatialdispositions with respect to the receiver aircraft 20 and/or the boomfuelling unit 310, optionally based on the type of the receiver aircraft20 (e.g. F-15, F-16, etc.) and/or the type of the boom fuelling unit310. Based on the comparison, the spatial disposition of the refuelingdevice 100 or the boom fuelling unit 310 with respect to the tankeraircraft 12 and/or to the fuel receptacle 22 of the receiver aircraft 20can be calculated. In some cases, a full or partial 3-D model of therefueling device 100 and/or the boom fuelling unit 310 can be calculatedbased on the depth and electromagnetic data received from the LIDAR unit351 and such full or partial 3-D model can be compared with one or morepre-stored generic full or partial 3-D models (e.g. one for each type ofaircraft and/or one for each type of boom fuelling unit). Based on thecomparison, the spatial disposition of the refueling device 100 or theboom fuelling unit 310 with respect to the tanker aircraft 12 and/or tothe fuel receptacle 22 of the receiver aircraft 20 can be calculated.The look up tables and/or the 3-D models can be stored for example onthe reference DR 1870.

It is to be noted that various other methods and techniques can be usedin order to determine the refueling device's 100 and/or the boomfuelling unit 310 spatial disposition with respect to the tankeraircraft 12 and/or to the fuel receptacle 22 of the receiver aircraft 20(it is to be noted that in some cases such determination is made, forexample, repeatedly).

It is to be noted that, with reference to FIG. 19, some of the blockscan be integrated into a consolidated block or can be broken down to afew blocks and/or other blocks may be added. Furthermore, in some cases,the blocks can be performed in a different order than described herein.It should be also noted that whilst the flow diagrams are described alsowith reference to the system elements that realizes them, this is by nomeans binding, and the blocks can be performed by elements other thanthose described herein.

Turning to FIG. 20, there is shown a flowchart illustrating a sequenceof operations carried out for providing maneuvering commands forpositioning a receiver aircraft within an engagement area relatedthereto, according to certain examples of the presently disclosedsubject matter. Maneuvering instructions module 1820 can be configuredto determine (it is to be noted that in some cases, as indicated herein,such determination is made, for example, repeatedly) the receiveraircraft's 20 spatial disposition with respect to the engagement arearelated thereto (block 2005), as further detailed with respect to FIG.22.

Following determination of the receiver aircraft's 20 spatialdisposition with respect to the engagement area related thereto,maneuvering instructions module 1820 can be configured to check if thereceiver aircraft 20 is positioned within the engagement area (block2010), based for example on current measurements from sensor/s 1890 asdescribed herein. In some examples, in case the receiver aircraft 20 ispositioned within the engagement area, and until the refueling device100 is engaged with the fuel receptacle 22 of the receiver aircraft 20(in some cases this process can continue until the refueling processends), the maneuvering instructions module 1820 can be configured toreturn to block 2005 and re-determine the receiver aircraft's 20 spatialdisposition with respect to the engagement area related thereto.

In some examples, in case the receiver aircraft 20 is not positionedwithin the engagement area, maneuvering instructions module 1820 can beconfigured to calculate maneuvering instructions for positioning thereceiver aircraft 20 within the engagement area (block 2020). It can beappreciated that once the maneuvering instructions module 1820determines the receiver aircraft's 20 spatial disposition with respectto the engagement area related thereto, it can also calculatemaneuvering instructions for positioning the receiver aircraft 20 withinthe engagement area related thereto. Maneuvering instructions module1820 can also provide the calculated maneuvering instructions forpositioning the receiver aircraft 20 (and, in some cases, an auto pilotsystem that controls the maneuvering of the receiver aircraft 20) withinthe engagement area related thereto to the pilot of the receiveraircraft 20 (block 2030) and return to block 2005.

It is to be noted that, in some cases, as indicated herein, maneuveringinstructions module 1820 can be configured to provide the maneuveringinstructions by using a light directing system. Such light directingsystem can be mounted, for example, on the tanker aircraft 12, at anylocation visible to the receiver aircraft 20 pilot. In some cases, thelight directing system can provide the pilot of the receiver aircraft 20with maneuvering instructions on three axes: forward-backward,left-right and up-down, thus enabling it to maneuver the receiveraircraft 20 to the engagement area 2110. Alternatively or additionally,the maneuvering instructions can be provided by using voice commands(e.g. by utilizing speakers, pilot headset, etc.) or by any other meansknown per se. In some cases, maneuvering instructions module 1820 can beconfigured to communicate the maneuvering instructions to an auto pilotsystem of the receiver aircraft 20, if such system exists.

It is to be noted that, with reference to FIG. 20, some of the blockscan be integrated into a consolidated block or can be broken down to afew blocks and/or other blocks may be added. Furthermore, in some cases,the blocks can be performed in a different order than described herein.It should be also be noted that whilst the flow diagrams are describedalso with reference to the system elements that realizes them, this isby no means binding, and the blocks can be performed by elements otherthan those described herein.

It is to be further noted that in some cases instead of monitoring thatthe receiver aircraft 20 is positioned within the engagement area, analternative light directing system can be used. Such an alternativelighting system can be designed to display alternative light indicationsdepending on the angle from which it is viewed. Thus, in some cases,viewing the light directing system from its bottom side can result indisplay of light in a certain color, looking at the same light directingsystem from its upper side can result in display of light in a secondcolor, looking at the same light directing system from its right sidecan result in display of light in a third color, and looking at the samelight directing system from its left side can result in display of lightin a fourth color. Additional angles can result in display of additionalcolors. When using such a light directing system, upon arrival of thereceiver aircraft 20 to the engagement area, the light directing systemcan be automatically directed to the receiver aircraft 20 (based on itscurrent determined spatial disposition) and provide a color indicationindicating that it is positioned within the engagement area. If thereceiver aircraft 20 does not maintain its position, the pilot willreceive appropriate color indications from the light directing system sothat he will be able to make the required corrections to maintain thereceiver aircraft's 20 spatial disposition.

Turning to FIG. 21, there is shown a flowchart illustrating a sequenceof operations carried out for providing steering commands to a refuelingdevice for maneuvering to an engagement enabling position, according tocertain examples of the presently disclosed subject matter.

When a non-aircraft-fixed in-flight refueling system is used steeringcontrol module 1830 can be configured to determine (it is to be notedthat in some cases, as indicated herein, such determination is made, forexample, repeatedly) the refueling device's 100 spatial disposition withrespect to the engagement enabling position (in which the boom member130 is in a predetermined maximal spaced and spatial relationship withrespect to the fuel receptacle 22 of the receiver aircraft 20) relatedthereto (block 2105), as further detailed with respect to FIG. 23.

Following determination of the refueling device's 100 spatialdisposition with respect to the engagement enabling position relatedthereto, steering control module 1830 can be configured to check if therefueling device 100 is positioned within the engagement enablingposition (block 2110). In case the refueling device 100 is positionedwithin the engagement enabling position (in which the boom member 130 isin a predetermined maximal spaced and spatial relationship with respectto the fuel receptacle 22 of the receiver aircraft 20), and at leastuntil the refueling device 100 is engaged with the fuel receptacle 22 ofthe receiver aircraft 20 (in some cases this process can continue untilthe refueling process ends), the steering control module 1830 can beconfigured to return to block 2105 and re-determine the refuelingdevice's 100 spatial disposition with respect to the engagement enablingposition related thereto.

In case the refueling device 100 is not positioned within the engagementenabling position (in which the boom member 130 is in a predeterminedmaximal spaced and spatial relationship with respect to the fuelreceptacle 22 of the receiver aircraft 20), steering control module 1830can be configured to calculate steering commands for maneuvering therefueling device 100 to an engagement enabling position, in which theboom member 130 is in a predetermined maximal spaced and spatialrelationship with respect to the fuel receptacle 22 of the receiveraircraft 20 (block 2120). It can be appreciated that once the steeringcontrol module 1830 determines the refueling device's 100 spatialdisposition with respect to an engagement enabling position relatedthereto, it can also calculate steering commands for maneuvering therefueling device 100 to an engagement enabling position related thereto.Steering control module 1830 can also provide the refueling device 100with calculated steering commands for maneuvering the refueling device100 to an engagement enabling position related thereto (block 2130) andreturn to block 2105. The steering commands can control the operation ofcomponents of the spatial control system 160 and/or the force generatingarrangement 190.

When utilizing an aircraft-fixed flying boom system, steering controlmodule 1830 can be configured to determine (it is to be noted that insome cases, as indicated herein, such determination is made, forexample, repeatedly) the boom fuelling unit 310 spatial disposition withrespect to the engagement enabling position (in which the boom member312 is in a predetermined maximal spaced and spatial relationship withrespect to the fuel receptacle 22 of the receiver aircraft 20) relatedthereto (block 2105), as further detailed with respect to FIG. 23.

Following determination of the boom fuelling unit 310 spatialdisposition with respect to the engagement enabling position relatedthereto, steering control module 1830 can be configured to check if theboom fuelling unit 310 is positioned within the engagement enablingposition (block 2110). In case the boom fuelling unit 310 is positionedwithin the engagement enabling position (in which the boom member 312 isin a predetermined maximal spaced and spatial relationship with respectto the fuel receptacle 22 of the receiver aircraft 20), and at leastuntil the boom fuelling unit 310 is engaged with the fuel receptacle 22of the receiver aircraft 20 (in some cases this process can continueuntil the refueling process ends), the steering control module 1830 canbe configured to return to block 2105 and re-determine the boom fuellingunit 310 spatial disposition with respect to the engagement enablingposition related thereto.

In case the boom fuelling unit 310 is not positioned within theengagement enabling position (in which the boom member 312 is in apredetermined maximal spaced and spatial relationship with respect tothe fuel receptacle 22 of the receiver aircraft 20), steering controlmodule 1830 can be configured to calculate alignment commands formaneuvering the boom fuelling unit 310 to an engagement enablingposition, in which the boom member 312 is in a predetermined maximalspaced and spatial relationship with respect to the fuel receptacle 22of the receiver aircraft 20 (block 2120). It can be appreciated thatonce the steering control module 1830 determines the boom fuelling unit310 spatial disposition with respect to an engagement enabling positionrelated thereto, it can also calculate alignment commands formaneuvering the boom fuelling unit 310 to an engagement enablingposition related thereto. Steering control module 1830 can also providethe boom fuelling unit 310 with calculated alignment commands formaneuvering the boom fuelling unit 310 to an engagement enablingposition related thereto (block 2130) and return to block 2105. Thealignment commands can control the operation of components of the motioncontrol system 330 and/or the mechanical connection 320 and/or thetelescoping aft section 314.

It is to be noted that, with reference to FIG. 21, some of the blockscan be integrated into a consolidated block or can be broken down to afew blocks and/or other blocks may be added. Furthermore, in some cases,the blocks can be performed in a different order than described herein.It should also be noted that whilst the flow diagrams are described alsowith reference to the system elements that realizes them, this is by nomeans binding, and the blocks can be performed by elements other thanthose described herein.

Turning to FIG. 22, there is provided a flowchart illustrating asequence of operations carried out for determining the receiveraircraft's spatial disposition with respect to the engagement arearelated thereto, according to certain examples of the presentlydisclosed subject matter. In some cases, maneuvering instructions module1820 can be configured to acquire an image of the receiver aircraft 20(block 2210).

For that purpose, in some cases, maneuvering instructions module 1820can be configured to utilize sensor control module 1810 for repeatedly(e.g. every pre-determined period) or continuously (e.g. in the form ofa video stream) acquiring an image of the area aft the refueling device100 and/or aft the tanker aircraft 12, at a predetermined Field of View.Such Field of View can depend, inter alia, on the distance from which areceiver aircraft 20 is to be identified. In some cases, the farther itis required to identify the receiver aircraft, the larger the Field ofView is.

It is to be noted that although reference in the description issometimes made to an image, any other data that can be indicative ofpresence of a receiver aircraft can be utilized mutatis mutandis (e.g.radar data, acoustic signature data, etc.). It is to be further notedthat in some cases, when reference is made to an image (throughout thedescription) it can also include an image based on data acquired by theLIDAR unit 351.

For the purpose of acquiring an image, sensor control module 1810 can beconfigured to utilize sensor 1890. In some cases, one or more sensor/s1890 can be mounted on the refueling device 100 and/or on the tankeraircraft 12. As indicated herein, in some cases the imaging system 150can be used as one or more of the sensor/s 1890. It is to be noted that,as indicated herein, the imaging system 150 can, in some cases, compriseone or more FLADAR units and/or one or more LIDAR units 351.

It can be appreciated that for acquiring an image of the receiveraircraft 100, the receiver aircraft 100 should be present in the sensedarea (e.g. the sensing volume 159 or the sensing volume 359). In somecases the receiver aircraft 20 is expected to approach the refuelingdevice 100 and/or the boom fuelling unit 310 and/or the fuel tanker 12for the refueling process to begin. In some cases, the approach ofreceiver aircraft 20 to the refueling device 100 and/or the boomfuelling unit 310 is made from a certain direction or through a virtualfunnel such as, for example, from the rear and bottom side of therefueling device 100 and/or the boom fuelling unit 310 and/or the fueltanker 12 while the pilot of the receiver aircraft 20 has a line ofsight to the refueling device 100 and/or the boom fuelling unit 310and/or the fuel tanker 12. However, in other cases, other directions ofapproach are also possible (e.g. approach from the front and bottom sideof the refueling device 100 and/or the boom fuelling unit 310 and/or thefuel tanker 12, etc.), depending, inter alia, on the characteristics ofthe receiver aircraft 20 (e.g. the location of the fuel receptacle 22 ofthe receiver aircraft 20, etc.).

In some cases, maneuvering instructions module 1820 can be configured toanalyze sensed images in order to determine if a receiver aircraft 20can be identified within the sensed image. It is to be noted that suchanalysis can be performed using various known methods and techniques,such as, in the case of digital images—image correlation, in the case ofLIDAR based images—comparison with look-up tables comprising referencedepth data and reference electromagnetic data relating to referencespatial dispositions with respect to the receiver aircraft, optionallybased on the type of the receiver aircraft 20 (e.g. F-15, F-16, etc.),etc.

In some cases, maneuvering instructions module 1820 can be configured tocause the signaling system to provide the pilot of the receiver aircraft20 with a notification indicating that its location with respect to theengagement area has been acquired. Such indication can be provided, forexample, by a signaling system (e.g. a lighting system mounted on therefueling device 100 and/or the boom fuelling unit 310 and/or on thetanker aircraft 12, etc.). Additionally or alternatively, the indicationcan be a voice indication provided to the pilot of the receiver aircraft20 (e.g. by utilizing speakers, pilot headset, etc.). Additionally oralternatively, the indication can be any other indication (includingvisual or voice indication) provided to the pilot of the receiveraircraft 20 (e.g. by utilizing speakers, pilot headset, a display, alight, etc.).

In some cases, maneuvering instructions module 1820 can be furtherconfigured to fetch configuration data (block 2220), including, interalia, data indicative of the engagement area specification. As detailedherein, the engagement area can be defined by various specificationsthat depend on several parameters, such as, for example, the length ofthe hose 52 (when a non-aircraft-fixed in-flight refueling system isused), the extension length of the telescoping aft section 314 (whenutilizing an aircraft-fixed flying boom system), the flight speed, theflight altitude, weather conditions, the fuel pressure within the hose52 (when a non-aircraft-fixed in-flight refueling system is used), thelocation of the fuel receptacle 22 of the receiver aircraft 20, etc.

In some cases, maneuvering instructions module 1820 can be furtherconfigured to fetch a reference image of a reference receiver aircraft(block 2230). In some cases the reference image is fetched inter aliaaccording to the fetched configuration data and/or the type of thereceiver aircraft 20 (e.g. F-15, F-16, etc.). Such a reference image canbe an image of an aircraft similar to the actual receiver aircraft 20,and in some cases of identical type as the actual receiver aircraft 20.If necessary, the maneuvering instructions module 1820 can obtaincurrent measurements for certain parameters in the configuration DR1860, to compute appropriate engagement area specifications.

It is to be noted that such a reference image should depict a scene inwhich the reference aircraft is positioned within the engagement areahaving the fetched specification (fetched in block 2220). In some cases,the reference image can depict a scene in which the reference aircraftis not positioned within the engagement area having the fetchedspecification, however the offset of the reference receiver aircraftfrom the engagement area can be calculated or alternatively is a-prioriknown.

Maneuvering instructions module 1820 can be further configured toutilize the reference image of a reference receiver aircraft within theengagement area having the fetched specification (or not within suchengagement area but with data of its offset from the engagement area)for calculating the relative spatial disposition of the receiveraircraft with respect to the engagement area (block 2240), for exampleusing methods and techniques known per se (such as, in the case ofdigital images, image correlation, etc.).

In some cases, 3-D models can be used instead of images. According tofurther examples, the reference DR 1870 can store one or more generic3-D models (e.g. one for each type of aircraft), and as part ofdetermining the spatial disposition of the receiver aircraft 20 withrespect to the engagement area, an appropriate 3-D model can be selected(for example according to the type of the receiver aircraft 20) and the3-D model can be adapted using current measurements (e.g. obtained bythe sensor 1890) and respective parameters of the 3-D model.

It is to be noted that various other methods and techniques can be usedin order to determine the receiver aircraft's 20 spatial dispositionwith respect to the engagement area.

One example of such alternative technique is using LIDAR. In such cases,the sensor 1890 can be a LIDAR unit 351 that can acquire the images asfurther detailed herein, inter alia with reference to FIGS. 30-32. Asindicated herein, the images obtained by the LIDAR unit 351 can compriseboth depth data and electromagnetic data within the sensing volume 359.In such cases, the depth and electromagnetic data can be compared withone or more look-up tables comprising reference depth data and referenceelectromagnetic data relating to reference spatial dispositions withrespect to the receiver aircraft, optionally based on the type of thereceiver aircraft 20 (e.g. F-15, F-16, etc.). Based on the comparison,the spatial disposition of the refueling device 100 and/or the boomfuelling unit 310 and/or the receiver aircraft 20 with respect to thetanker aircraft 12 can be calculated. In some cases, a full or partial3-D model of the receiver aircraft 20 and/or the refueling device 100and/or the boom fuelling unit 310 can be calculated based on the depthand electromagnetic data received from the LIDAR unit 351 and such fullor partial 3-D model can be compared with one or more pre-stored genericfull or partial 3-D models (e.g. one for each type of aircraft). Basedon the comparison, the spatial disposition of the refueling device 100and/or the boom fuelling unit 310 and/or the receiver aircraft 20 withrespect to the tanker aircraft 12 can be calculated. The look up tablesand/or the 3-D models can be stored for example on the reference DR1870.

It is to be noted that, with reference to FIG. 22, some of the blockscan be integrated into a consolidated block or can be broken down to afew blocks and/or other blocks may be added. Furthermore, in some cases,the blocks can be performed in a different order than described herein.It should be also be noted that whilst the flow diagrams are describedalso with reference to the system elements that realizes them, this isby no means binding, and the blocks can be performed by elements otherthan those described herein.

Turning to FIG. 23 there is provided a flowchart illustrating a sequenceof operations carried out for determining the refueling device's 100 (orboom fuelling unit 310) spatial disposition with respect to theengagement enabling position, according to certain examples of thepresently disclosed subject matter. In some cases, steering controlmodule 1830 can be configured to acquire an image of the receiveraircraft 20 (block 2310), and, in some cases, more specifically, of thearea of the fuel receptacle 22 of the receiver aircraft 20.

For that purpose, in some cases, steering control module 1830 can beconfigured to utilize sensor control module 1810 for repeatedly (e.g.every pre-determined period) or continuously acquiring an image (it isto be noted again that although reference in the description is made toan image, any other data that can be indicative of presence of areceiver aircraft can be utilized mutatis mutandis. It is to be furthernoted that in some cases, when reference is made to an image it can alsoinclude an image based on data acquired by the LIDAR unit 351) of thearea aft the refueling device 100 or boom fuelling unit 310, at apredetermined Field of View. Such Field of View can depend, inter alia,on the distance from which a receiver aircraft 20, and more specificallya fuel receptacle 22 thereof, is to be identified. In some cases, thefarther it is required to identify the receiver aircraft, and morespecifically a fuel receptacle 22 thereof, the larger the Field of Viewis.

For the purpose of acquiring an image, sensor control module 1810 can beconfigured to utilize sensor 1890. In some cases, one or more sensor/s1890 can be mounted on the refueling device 100 and/or the boomrefueling unit 310 and/or on the tanker aircraft 12. As indicatedherein, in some cases the imaging system 150 can be used as one or moreof the sensor/s 1890. It is to be noted that, as indicated herein, theimaging system 150 can, in some cases, comprise one or more FLADAR unitsand/or one or more LIDAR units 351.

It can be appreciated that for acquiring an image of the receiveraircraft 20, and more specifically a fuel receptacle 22 thereof, thereceiver aircraft 20, and more specifically a fuel receptacle 22thereof, must be present in the sensed area (e.g. the sensing volume159). In some cases, the receiver aircraft 20 is expected to bepositioned within the engagement area related thereto.

In some cases steering control module 1830 can be configured to analyzea sensed image in order to determine if a receiver aircraft 20, and morespecifically a fuel receptacle 22 thereof, can be identified within thesensed image. A series of images can be analyzed, each substantiallyimmediately after it has been captured (for example as describedherein), in order for the steering control module 1830 to be able toprovide steering or alignment commands that are based on the actual(dynamic) relative position of the refueling device 100 and/or the boomfuelling unit 310 and the engagement enabling position.

In some cases, 3-D models can be used instead of images. According tofurther examples, the reference DR 1870 can store one or more generic3-D models (e.g. one for each type of aircraft), and as part ofdetermining the spatial disposition of the refueling device 100 and/orthe boom fuelling unit 310 with respect to the engagement enablingposition, an appropriate 3-D model can be selected (for exampleaccording to the type of the receiver aircraft 20) and the 3-D model canbe adapted using current measurements (e.g. obtained by the sensor/s1890) and respective parameters of the 3-D model.

It is to be noted that such analysis can be performed using variousknown methods and techniques, such as, in the case of digitalimages—image correlation, in the case of LIDAR based images—comparisonwith look-up tables comprising reference depth data and referenceelectromagnetic data relating to reference spatial dispositions withrespect to the receiver aircraft, optionally based on the type of thereceiver aircraft 20 (e.g. F-15, F-16, etc.), etc.

In some cases, steering control module 1830 can be further configured tofetch configuration data (block 2320), including, inter alia, dataindicative of the engagement enabling position specification. Asdetailed herein, the engagement enabling position can be defined by apredetermined maximal spaced and spatial relationship with respect tothe fuel receptacle 22 of the receiver aircraft 20. As further indicatedherein, such configuration data can depend on several parameters, suchas, for example, the length of the hose 52 (when a non-aircraft-fixedin-flight refueling system is used), the extension length of thetelescoping aft section 314 (when utilizing an aircraft-fixed flyingboom system), the flight speed, the flight altitude, weather conditions,the fuel pressure within the hose 52 (when a non-aircraft-fixedin-flight refueling system is used), the location of the fuel receptacle22 of the receiver aircraft 20, etc. The configuration data is fetchedaccording to current measurements and respective parameters stored inassociation with each set of configuration data.

In some cases, steering control module 1830 can be further configured tofetch a reference image of a reference receiver aircraft, and morespecifically a fuel receptacle thereof (block 2330). In some cases thereference image is fetched inter alia according to the fetchedconfiguration data (which, in turn, was fetched according to currentmeasurements and respective parameters stored in association with eachset of configuration data). Such a reference image can be an image of anaircraft, and more specifically a fuel receptacle thereof, similar, andin some cases identical to, the actual receiver aircraft 20, and morespecifically, an actual fuel receptacle 22 of the actual receiveraircraft 20.

It is to be noted that such a reference image should depict a scene inwhich the reference aircraft, and more specifically a fuel receptaclethereof, is positioned within an engagement enabling position having thefetched specification (fetched in block 2320). In some cases, thereference image can depict a scene in which the reference aircraft, andmore specifically a fuel receptacle thereof, is not positioned withinthe engagement enabling position having the fetched specification,however the offset of the reference receiver aircraft from theengagement enabling position can be calculated or alternatively isa-priori known.

In some cases, steering control module 1830 can be further configured toutilize the reference image of a reference receiver aircraft, and morespecifically a fuel receptacle thereof, within the engagement areahaving the fetched specification (or not within such engagement area butwith data of its offset from the engagement area) for calculating therelative spatial disposition of the receiver aircraft 20, and morespecifically the fuel receptacle 22 thereof, with respect to anengagement enabling position (block 2340), for example using methods andtechniques known per se (such as, in the case of digital images, imagecorrelation, etc.).

In some cases, 3-D models can be used instead of images. According tofurther examples, the reference DR 1870 can store one or more generic3-D models (e.g. one for each type of aircraft), and as part ofdetermining the spatial disposition of the refueling device 100 withrespect to engagement enabling position, an appropriate 3-D model can beselected (for example according to the type of the receiver aircraft 20)and the 3-D model can be adapted using current measurements (e.g.obtained by the sensor 1890) and respective parameters of the 3-D model.

It is to be noted that various other methods and techniques can be usedin order to determine the refueling device 100 and/or the boom fuellingunit 310 spatial disposition with respect to the engagement area.

One example of such alternative technique is using LIDAR. In such cases,the sensor 1890 can be a LIDAR unit 351 that can acquire the images asfurther detailed herein, inter alia with reference to FIG. 30-32. Asindicated herein, the images obtained by the LIDAR unit 351 can compriseboth depth data and electromagnetic data within the sensing volume 359.In such cases, the depth and electromagnetic data can be compared withone or more look-up tables comprising reference depth data and referenceelectromagnetic data relating to reference spatial dispositions withrespect to the receiver aircraft, optionally based on the type of thereceiver aircraft 20 (e.g. F-15, F-16, etc.). Based on the comparison,the spatial disposition of the refueling device 100 and/or the boomfuelling unit 310 and/or the receiver aircraft 20 with respect to thetanker aircraft 12 can be calculated. In some cases, a full or partial3-D model of the receiver aircraft 20 and/or the refueling device 100and/or the boom fuelling unit 310 can be calculated based on the depthand electromagnetic data received from the LIDAR unit 351 and such fullor partial 3-D model can be compared with one or more pre-stored genericfull or partial 3-D models (e.g. one for each type of aircraft). Basedon the comparison, the spatial disposition of the refueling device 100and/or the boom fuelling unit 310 and/or the receiver aircraft 20 withrespect to the tanker aircraft 12 can be calculated. The look up tablesand/or the 3-D models can be stored for example on the reference DR1870.

It is to be noted that, with reference to FIG. 23, some of the blockscan be integrated into a consolidated block or can be broken down to afew blocks and/or other blocks may be added. Furthermore, in some cases,the blocks can be performed in a different order than described herein.It should be also be noted that whilst the flow diagrams are describedalso with reference to the system elements that realizes them, this isby no means binding, and the blocks can be performed by elements otherthan those described herein.

Looking, by way of example, at FIG. 28, there is shown an illustrationof an example of a sensed image indicating that the refueling device isnot positioned in an engagement enabling position, according to certainexamples of the presently disclosed subject matter. In some cases, thesensed image of the receiver aircraft 20, and more specifically a fuelreceptacle 22 thereof, and the reference image of the reference receiveraircraft, and more specifically a fuel receptacle thereof, can containsome elements (e.g. 2810, 2820, 2830, 2840, etc.) that enabledetermination of the sensed image offset from the reference image(thereby enabling determination of the offset of the refueling device100 or the boom fuelling unit 310 from an engagement enabling position,in which the boom member 130 or boom member 312 is in a predeterminedmaximal spaced and spatial relationship with respect to the fuelreceptacle 22 of the receiver aircraft 20). It is to be noted thatvirtual cross 2850 indicates the center of the image. Such elements(e.g. 2810, 2820, 2830, 2840) can be used for example by various knownper se image correlation algorithms in order to determine the spatialdisposition of the receiver aircraft 20, and more specifically the fuelreceptacle 22 thereof, with respect to an engagement enabling position.The illustration of FIG. 28 is provided for clarity of explanation onlyand is by no means binding.

Attention is now drawn to FIG. 29, showing an illustration of an exampleof a reference image indicating that the refueling device is positionedin an engagement enabling position, according to certain examples of thepresently disclosed subject matter. Looking at the illustration, it canbe appreciated that the fuel receptacle of a receiver aircraft should bealigned with the cross 2850 (that indicates the center of the image) andthat elements 2810, 2820, 2830, and 2840 should also be aligned with thecross 2850 vertical and horizontal axis, thus indicating that arefueling device is positioned in an engagement enabling position, inwhich the boom member 130 or boom member 312 is in a predeterminedmaximal spaced and spatial relationship with respect to the fuelreceptacle 22 of the receiver aircraft 20. It can be appreciated thatthere is an offset between the sensed image shown in FIG. 28 and thereference image shown in FIG. 29, thus indicating that at the time thesensed image shown in FIG. 28 was sensed, the refueling device 100 orthe boom fuelling unit 310 was not in an engagement enabling position.The illustration of FIG. 29 is provided for clarity of explanation onlyand is by no means binding.

It has been indicated herein that when a non-aircraft-fixed in-flightrefueling system is used the engagement enabling position is a positionfrom which utilization of the force generating arrangement 190 enablesthe nozzle 135 to engage with the fuel receptacle 22 of the receiveraircraft 20. When utilizing an aircraft-fixed flying boom system, theengagement enabling position is a position from which the nozzle 316 isable to engage with the fuel receptacle 22 of the receiver aircraft 20.Therefore, in some cases, there can be more than one engagement enablingposition that meets such criteria and thus, in some cases, a certainoffset between the sensed image and the reference image can be allowed,as long as the refueling device is in a position from which, when anon-aircraft-fixed in-flight refueling system is used, utilization ofthe force generating arrangement 190 enables the nozzle 135 to engagewith the fuel receptacle 22 of the receiver aircraft 20 or from which,when utilizing an aircraft-fixed flying boom system, the nozzle 316 isable to engage with the fuel receptacle 22 of the receiver aircraft 20.

It is to be noted that various other methods and techniques can be usedin order to determine the receiver aircraft's 20 spatial dispositionwith respect to the engagement enabling position, including the knownper se 3-D modeling adaptation and/or the selection of the referenceimage which provides the highest correlation to the sensed data.

Operation Mode II

In this operation mode, once the tanker aircraft 12 and receiveraircraft 20 are in close proximity and flying in formation, with thereceiver aircraft 20 at a position behind the tanker aircraft 12, therefueling device is flown into engagement with the fuel receptacle 22 ofthe receiver aircraft 20 by an operator.

In a first example of Operation Mode II, the operator is stationed inthe tanker aircraft 12, which comprises a suitable control stationoperatively connected to the refueling device, which can be refuelingdevice 100 according to the first example or alternative variationsthereof, or refueling device 200 according to the second example oralternative variations thereof, or a refueling device according to othersuitable examples thereof according to the first aspect of the presentlydisclosed subject matter. The control station comprises a display devicefor suitably displaying data relating to the spatial disposition of therefueling device at least with respect to the receiver aircraft 20 andthe fuel receptacle 22 thereof, and an output device for providingcontrol signals to the refueling device for controlling the flightthereof.

For example, and referring to refueling device 100 according to thefirst example or alternative variations thereof, the display device cancomprise a screen display that displays real time images (2D, and/orstereoscopic images, and/or 3D images), for example in video streams,provided by the imaging system 150. Additionally or alternatively, suchimaging can be provided or augmented via suitable cameras or otherimaging units, provided on the tanker aircraft 12 and/or the receiveraircraft 20 and/or any other suitable air vehicle in the vicinity of therefueling device 100, and thus in at least some such examples therefueling device 100 can omit the imaging system 150.

The output device can comprise, for example, a joystick that ishand-manipulated by the operator to provide the required control signalsto the spatial control system 160, in particular the controllableaerodynamic surfaces thereof, to provide the required design angleθ_(des) between the boom axis 131 and the forward direction A, whileflying the refueling device 100 into proximity with the receiveraircraft 20 and the fuel receptacle 22 thereof.

The operator first ensures that the refueling device 100 is being towedbehind the tanker aircraft 12 at a suitable distance therefrom, and cancontrol this spacing by extending or retracting the hose 52 with respectto the tanker aircraft 12.

When the operator determines that the nozzle 135 is properly alignedwith the fuel receptacle 22 (the boom member 130 and boom axis 131 beingat the design angle θ_(des) to the forward direction A) and sufficientlyclose thereto, i.e., at the engagement enabling position at apredetermined spacing from the receiver aircraft, said boom axis beingaligned in an engagement enabling orientation at said spaced position,the operator provides a suitable control signal to the refueling device100 to activate the force generating arrangement 190, i.e., by deployingthe air brakes 195, 196, generating a force along boom axis 131 thateffectively pushes the nozzle into engagement with the receptacle 22. Inother words, once the refueling device 100 is at the aforesaidengagement enabling orientation and spaced position, the boom member issubsequently moved along said boom axis towards the receiver aircraftfor enabling fuel communication therebetween. Movement of the boommember can be effected in one of two ways, or combination thereof: therefueling device 100 remains in the spaced position, and the boom member130 is extended telescopically; the boom member 130 can be in theretracted or extended position, and the refueling device 100 is bodilymoved towards the receiver aircraft for enabling fuel communicationtherebetween.

Thereafter, the air brakes 195, 196 are retracted, and fuel is pumped tothe receiver aircraft 20 from the tanker aircraft 12. The refuelingdevice 100 can be automatically or manually controlled to maintain therequired design angle θ_(des) between then boom axis 131 and the forwarddirection A during refueling.

Once refueling is completed, the operator disengages the nozzle 135 fromthe fuel receptacle 22 and flies the refueling device 100 at least to asafe position away from the receiver aircraft 20, and/or the receiveraircraft 20 maneuvers to such a position, and the refueling device 100can be retracted back into the tanker aircraft 12, or reused withanother receiver aircraft 20.

It is to be noted that the same operator can carry out Operation Mode IIwith each of the plurality of refueling systems 50 of the tankeraircraft 12. Alternatively, the tanker aircraft 12 can comprise adedicated control station operatively connected to each refueling device100, and operated by a respective dedicated operator; thus differentoperators control each of the refueling devices 100.

In an alternative variation of this example of Operation Mode II, theoperator is stationed in another aircraft different from the receiveraircraft 20 or tanker aircraft 12, or is located in a ground station,and Operation Mode II can be carried out in a similar; manner to thatdescribed above for the first example, mutatis mutandis, with the maindifference that the operator receives the data relating to the spatialdisposition of the refueling device at least with respect to thereceiver aircraft 20 and the fuel receptacle 22 thereof, and providescontrol signals to the refueling device for controlling the flightthereof, via a suitable communications link respect to the refuelingdevice 100, which is correspondingly equipped with suitablecommunication system.

In another alternative variation of this example of Operation Mode II,the operator is stationed in the receiver aircraft 20 rather than intanker aircraft 12, and Operation Mode II can be carried out in asimilar; manner to that described above for the first example, mutatismutandis, with the main difference that the operator receives the datarelating to the spatial disposition of the refueling device at leastwith respect to the receiver aircraft 20 and the fuel receptacle 22thereof, and provides control signals to the refueling device forcontrolling the flight thereof, via a suitable communications link withrespect to the refueling device 100, and the receiver aircraft 20 andthe refueling device 100 are each correspondingly equipped with asuitable communication system. Alternatively, in at least somecircumstances, the operator can have the refueling device 100 inparticular the boom member 130 and nozzle 135, and the fuel receptacle22 in the operator's visual field of view, and does not require theaforesaid spatial disposition data in order to control the refuelingdevice 100, and thus in such cases the refueling device 100 can omit theimaging system 150.

Clearly, Operation Mode II can be applied to other variations of thefirst example of refueling device 100, or to the second example ofrefueling device 200 or alternative variations thereof, in a similarmanner to that described above for the first example of refueling device100, mutatis mutandis.

It is to be noted that according to Operation Mode I and/or OperationMode II, the refueling unit can be selectively controlled to adopt analigned configuration with the hose 52. By way of non-limiting example,such a situation is illustrated in FIG. 2 for the fuselage-mountedsystem 50. Such a configuration can include controlling the spatialcontrol system 160 to align the longitudinal axis 111 with the forwarddirection A in the case of the first example of refueling device 100 oralternative variations thereof, or maintaining the boom 230 in aretracted configuration accommodated in body 210 in the case of thesecond example of refueling device 200 or alternative variationsthereof, for example.

Operation Mode III

In this operation mode, the tanker aircraft 12 and receiver aircraft 20are maneuvered to be in close proximity and flying in formation, withthe receiver aircraft 20 at a position behind the tanker aircraft 12. Itis first ensured that the refueling device 100 is being towed behind thetanker aircraft 12 at a suitable distance therefrom, and an operator(typically in the tanker aircraft) can control this spacing by extendingor retracting the hose 52 with respect to the tanker aircraft 12.

In a first example of Operation Mode III, the refueling device 100 isnot flown or controlled per se, but attains a stable configuration withthe boom member 135 at the required angle with respect to the forwarddirection A, design angle θ_(des). Accordingly the refueling device 100can optionally omit the controllable spatial control system 160, andinstead comprises a suitable configuration that provides stability tothe boom member 135 at this spatial disposition.

The receiver aircraft 20 maneuvers to a position where it can engage thenozzle to the receiver aircraft fuel receptacle, and when an operator inthe receiver aircraft (for example the pilot) determines that the nozzle135 is properly aligned with the fuel receptacle 22 and sufficientlyclose thereto, the operator provides a suitable control signal to therefueling device 100 to activate the force generating arrangement 190,i.e., by deploying the air brakes 195, 196, generating a force alongboom axis 131 that effectively pushes the nozzle into engagement withthe receptacle 22. Thereafter, the air brakes 195, 196 are retracted,fuel is pumped to the receiver aircraft 20 from the tanker aircraft 12,and the refueling device 100 maintains the required design angle θ_(des)between then boom axis 131 and the forward direction A during refueling.

The receiver aircraft can comprise a display device for suitablydisplaying data relating to the spatial disposition of the refuelingdevice at least with respect to the receiver aircraft 20 and the fuelreceptacle 22 thereof.

For example, and referring to refueling device 100 according to thefirst example or alternative variations thereof, the display device cancomprise a screen display that displays to the operator (for example thepilot or navigator of the receiver aircraft) real time images (2D,and/or stereoscopic images, and/or 3D images), for example in videostreams, provided by the imaging system 150. Additionally oralternatively, such imaging can be provided or augmented via suitablecameras or other imaging units, provided on the tanker aircraft 12and/or the receiver aircraft 20 and/or any other suitable air vehicle inthe vicinity of the refueling device 100, and thus in at least some suchexamples the refueling device 100 can omit the imaging system 150.

Alternatively, in at least some circumstances, the operator can have therefueling device 100 in particular the boom member 130 and nozzle 135,and the fuel receptacle 22 in the operator's visual field of view, anddoes not require the aforesaid spatial disposition data, and thus insuch examples the refueling device 100 can omit the imaging system 150.

In at least some circumstances, the operator/pilot can maneuver thereceiver aircraft 12 such as to provide a suitable force via the fuelreceptacle 22 to engage the nozzle 135 thereto, or alternatively thereceiver aircraft can comprise a suitable arrangement configured forengage the nozzle 135 to the fuel receptacle 22 without the need togenerate such a force, and thus in such examples the refueling device100 can omit the force generating arrangement 190.

Once refueling is completed, the operator disengages the nozzle 135 fromthe fuel receptacle 22 and the receiver aircraft 20 maneuvers to atleast a safe position spaced from the refueling device 100, and therefueling device 100 can be retracted back into the tanker aircraft 12,or reused with another receiver aircraft 20.

It is to be noted that Operation Mode III can be carried out with eachof the plurality of refueling systems 50 of the tanker aircraft 12.

Clearly, Operation Mode III can be applied to other variations of thefirst example of refueling device 100, or to the second example ofrefueling device 200 or alternative variations thereof in a similarmanner to that described above for the first example of refueling device100, mutatis mutandis.

Reference is made to FIG. 32, showing a schematic illustration of ascene sensed by the LIDAR unit according to certain examples of thepresently disclosed subject matter.

In this example, the LIDAR unit 351 scans the sensing volume 359, whileat least one scan line intersects with the fuel receptacle 22 (oranother recognizable part from which the position and orientation of thefuel receptacle 22 can be estimated) of the receiver aircraft 20 and atleast one scan line intersects with a certain location on the boommember 312 (e.g. a boom tip marker 340 located thereon) or refuelingdevice 100.

It is to be noted that although in this example the scan lines arehorizontal alternative scan pattern can be used as well.

Turning to FIG. 33, there is shown a representation of the depth andelectromagnetic data relating to the boom refueling device and to thefuel receptacle of the receiver aircraft as acquired by the LIDAR unitaccording to certain examples of the presently disclosed subject matter.

The boom fueling device 310 electromagnetic data, shown as element 405in the figure, shows that at a certain area, having a certain width,within a certain scan line of the LIDAR unit 351, the electromagneticvalue was higher than the electromagnetic value in its surrounding area,thus indicating that the boom member 312 (or, sometimes, morespecifically, boom tip marker 340) is located in this area. As indicatedabove, in some cases the intensity can be affected, for example, by afuel receptacle marker 342 located at a pre-determined location on theboom member 312 and causing strong intensity reflection of therespective beam B2 when illuminated by beam B1, as compared with thereflection intensity obtained from other surfaces of the boom fuellingunit 310, for example.

The boom fueling device 310 depth data, shown as element 410 in thefigure, shows that at a certain area, having a certain width, within acertain scan line of the LIDAR unit 351, the depth value was lower thanthe depth value in its surrounding area, thus also indicating that theboom member 312 is located in this area. The area in which the boommember 312 is located is closer to the LIDAR unit 351 in comparison toits surrounding area, and thus the time interval between the outgoingbeams and the return beams associated with the area comprising the boommember 312 is lower than the time interval between the outgoing beamsand the return beams associated with areas surrounding it.

The fuel receptacle 22 electromagnetic data, shown as element 415 in thefigure, shows that at a certain area, having a certain width, within acertain scan line of the LIDAR unit 351, the electromagnetic value waslower than the electromagnetic value in its surrounding area, thusindicating that the fuel receptacle is located in this area. Theelectromagnetic value is lower at that area, for example since the fuelreceptacle 22 located within the corresponding area is deeper than itssurrounding area.

As indicated above, in some cases the intensity can be affected by afuel receptacle marker 342 comprised on the receiver aircraft 20 in apre-determined location with respect to the fuel receptacle 22 thereofand causing strong intensity reflection of the respective beam B2 whenilluminated by beam B1, as compared with the reflection intensityobtained from other surfaces of the receiver aircraft 20, for example.

The fuel receptacle 22 depth data, shown as element 420 in the figure,shows that at a certain area, having a certain width, within a certainscan line of the LIDAR unit 351, the depth value was higher than thedepth value in its surrounding area, thus also indicating that the fuelreceptacle 22 is located in this area. The area in which the fuelreceptacle 22 is located is farther from the LIDAR unit 351 incomparison to its surrounding area, and thus the time interval betweenthe outgoing beams and the return beams associated with the areacomprising the boom member 312 is lower than the time interval betweenthe outgoing beams and the return beams associated with areassurrounding it.

It is to be noted that, as any person of ordinary skill in the art canappreciate, the depths and width of the fuel receptacle depth dataand/or the boom fueling device depth data can enable calculation of thespatial dispositions of the fuel receptacle 22 and/or the boom fuelingdevice 310 (and its tip) with respect to the fuel tanker 12 and withrespect to each other.

It is to be further noted that the boom fueling device 310electromagnetic data shown as element 405, the boom fueling device 310depth data shown as element 410, the fuel receptacle 22 electromagneticdata shown as element 415 and the fuel receptacle 22 depth data shown aselement 420 can be compared with pre-stored look-up tables comprisingreference depth data and reference electromagnetic data relating toreference spatial dispositions with respect to the receiver aircraft,optionally based on the type of the receiver aircraft 20 (e.g. F-15,F-16, etc.), thus enabling calculation of various spatial relationships,e.g. between any two of the following: the boom fueling device 310, thefuel receptacle 22, the refueling device 100, the receiver aircraft 20,the engagement enabling position, the engagement area.

It is to be further noted that although the description of FIG. 33refers to a boom fueling device 310 the same also applies to anon-aircraft-fixed in-flight refueling system (e.g. refueling device100, etc.).

In the method claims that follow, alphanumeric characters and Romannumerals used to designate claim steps are provided for convenience onlyand do not imply any particular order of performing the steps.

It should be noted that the word “comprising” as used throughout theappended claims is to be interpreted to mean “including but not limitedto”.

While there has been shown and disclosed examples in accordance with thepresently disclosed subject matter, it will be appreciated that manychanges may be made therein without departing from the spirit of thepresently disclosed subject matter.

It is to be understood that the presently disclosed subject matter isnot limited in its application to the details set forth in thedescription contained herein or illustrated in the drawings. Thepresently disclosed subject matter is capable of other embodiments andof being practiced and carried out in various ways. Hence, it is to beunderstood that the phraseology and terminology employed herein are forthe purpose of description and should not be regarded as limiting. Assuch, those skilled in the art will appreciate that the conception uponwhich this disclosure is based may readily be utilized as a basis fordesigning other structures, methods, and systems for carrying out theseveral purposes of the present presently disclosed subject matter.

It will also be understood that the system according to the presentlydisclosed subject matter may be a suitably programmed computer.Likewise, the presently disclosed subject matter contemplates a computerprogram being readable by a computer for executing the method of thepresently disclosed subject matter. The presently disclosed subjectmatter further contemplates a machine-readable memory tangibly embodyinga program of instructions executable by the machine for executing themethod of the presently disclosed subject matter.

1. A refueling device for use in in-flight refueling operation,comprising: (a) a body configured for being towed by a tanker aircraftvia a fuel hose at least during in-flight refueling operation, andcomprising a boom member having a boom axis and configured to enablefuel to be transferred from said fuel hose to a receiver aircraft alongsaid axis during said in-flight refueling operation; (b) spatial controlsystem configured for selectively ensuring maintaining a desirednon-zero angular disposition between said boom axis and a forwarddirection at least when said refueling device is towed by the tankeraircraft in said forward direction via said fuel hose.
 2. The refuelingdevice according to claim 1, the boom member comprising a fuel deliverynozzle, and the receiver aircraft comprising a fuel receptacleconfigured for engaging with the fuel delivery nozzle to enablerefueling of the receiver aircraft.
 3. The refueling device according toany one of claims 1 to 2, wherein said angular disposition is definedabout at least one of a pitch axis, a yaw axis and a roll axis of saidrefueling device.
 4. The refueling device according to any one of claims1 to 2, wherein said angular disposition is such as to ensure that theboom axis is at a predetermined design angle with respect to thereceiver aircraft.
 5. The refueling device according to any one ofclaims 1 to 4, wherein said design angle is about 30°.
 6. The refuelingdevice according to any one of claims 1 to 5, wherein said refuelingdevice is configured for maintaining said desired non-zero angulardisposition between said boom axis and said forward direction at leastprior to engagement of said fuel delivery nozzle with a fuel receptacleof a receiver aircraft that is flying in formation aft of the tankeraircraft.
 7. The refueling device according to any one of claims 1 to 6,wherein said spatial control system is further configured forselectively providing control moments in at least one of pitch, yaw androll wherein to enable the refueling device to be flown while towed bythe tanker aircraft in said forward direction via said fuel hose.
 8. Therefueling device according to any one of claims 1 to 7, wherein saidbody comprises a longitudinal axis, and said boom member is pivotablymounted with respect to said body, and pivotable between a retractedposition and a deployed position, wherein in said retracted positionsaid boom axis is at a smaller angular disposition with respect to saidlongitudinal axis than in said deployed position.
 9. The refuelingdevice according to claim 8, wherein in said retracted position saidboom axis is at an angular disposition with respect to said longitudinalaxis of between 0° and 15°, and wherein in said deployed position, saidangular disposition is greater than 15°.
 10. The refueling deviceaccording to claim 8 or claim 9, wherein in said deployed position saidboom axis is at an angular disposition with respect to said longitudinalaxis between 20° to 40°.
 11. The refueling device according to any oneof claims 8 to 10, wherein said boom member is in said deployed positionduring said in-flight refueling operation.
 12. The refueling deviceaccording to any one of claims 1 to 7, wherein said body comprises alongitudinal axis, and said boom member is mounted with respect to saidbody, such as to maintain a generally parallel spatial dispositionbetween said boom axis and said longitudinal axis at least during saidin-flight refueling operation.
 13. The refueling device according to anyone of claims 1 to 12, wherein said spatial control system comprisesselectively controllable aerodynamic control system.
 14. The refuelingdevice according to claim 13, wherein said selectively controllableaerodynamic control system comprises a forward set of aerodynamiccontrol surfaces mounted to said body, and an aft set of aerodynamiccontrol surfaces mounted to said body in longitudinally aft spacedrelationship with respect to said forward set of aerodynamic controlsurfaces.
 15. The refueling device according to claim 14, wherein saidforward set of aerodynamic control surfaces comprises a canardconfiguration, and said aft set of aerodynamic control surfacescomprises one or more wing elements
 16. The refueling device accordingto claim 14 or claim 15, wherein said aft set of aerodynamic controlsurfaces comprises an H-tail configuration, comprising two verticalstabilizers, one each on either side of a horizontal stabilizer.
 17. Therefueling device according to any one of claims 14 to 16, wherein saidforward set of aerodynamic control surfaces comprises at least four saidcontrol surfaces mounted to said body in cruciform configuration. 18.The refueling device according to any one of claims 1 to 17, whereinsaid spatial control system is configured for enabling the refuelingdevice to be steered in one, or two, or three degrees of freedom intranslation, and in one, or two, or three degrees of freedom inrotation, independently of the tanker aircraft or of the refuelingaircraft.
 19. The refueling device according to claim 18, wherein saidspatial control system is configured for providing at least one of: oneor more of: sideslip, up/down translation, forward-aft translation,relative to the tanker aircraft and/or to the refueling aircraft,independently of rotational moments in roll pitch and/or yaw; rotationalmoments in one or more of roll pitch and/or yaw, relative to the tankeraircraft and/or to the refueling aircraft, independently of sideslip,up/down translation, forward-aft translation.
 20. The refueling deviceaccording to any one of claims 1 to 19, wherein said spatial controlsystem is configured for providing an angle of attack for the body withrespect to the forward direction, between −10° and +10°.
 21. Therefueling device according to any one of claims 1 to 20, furthercomprising an aerodynamic stabilizer arrangement, different from thespatial control system.
 22. The refueling device according to claim 21,wherein said aerodynamic stabilizer arrangement is in the form of adrogue structure having a stowed configuration, in which droguestructure generates a minimum drag, and a deployed configuration indrogue structure generates greater drag than in the inactiveconfiguration.
 23. The refueling device according to any one of claims 1to 22, further comprising a force generating arrangement configured forselectively generating a force along said boom axis in a directiontowards said fuel delivery nozzle.
 24. The refueling device according toclaim 23, wherein said force generating arrangement comprises aselectively actuable drag inducing arrangement.
 25. The refueling deviceaccording to any one of claims 23 to 24, wherein said force generatingarrangement is configured for selectively generating said force alongsaid boom axis in a direction towards said fuel delivery nozzleresponsive to said fuel delivery nozzle being in predetermined proximityto the fuel receptacle of the receiver aircraft wherein to force saidfuel delivery nozzle into engagement with the fuel receptacle.
 26. Therefueling device according to any one of claims 1 to 25, said bodycomprising a fuel delivery lumen configured for fluid communication withsaid fuel hose and said boom member at least during the in-flightrefueling operation, wherein said body comprises a coupling having ahose interface configured for connecting said lumen to the fuel hose,said coupling configured for allowing relative rotation between the hoseand said body in at least one degree of freedom while maintaining saidfuel communication.
 27. The refueling device according to claim 26,wherein said coupling is configured for allowing relative rotationbetween the hose and said body in at least two degrees of freedom or inthree degrees of freedom.
 28. The refueling device according to any oneof claims 26 to 27, wherein at least one said rotational degree offreedom has the respective axis of rotation generally orthogonal to aplane defining said non-zero angular disposition between said boom axisand said forward direction.
 29. The refueling device according to anyone of claims 26 to 28, wherein said coupling comprises a universalcoupling.
 30. The refueling device according to any one of claims 1 to29, wherein said boom member is selectively reversibly telescopicallydeployable along said boom axis with respect to said body.
 31. Therefueling device according to any one of claims 1 to 30, furthercomprising a data acquisition system configured for providing spatialdata relating to a relative spatial disposition between said fueldelivery nozzle and said fuel receptacle, to enable selectivelycontrolling the refueling device to provide automatic or autonomous ormanual engagement of the fuel delivery nozzle to the fuel receptacle ofthe receiver aircraft.
 32. The refueling device according to claim 31,wherein said data acquisition system comprises an imaging systemconfigured for providing said spatial data including image datacorresponding to a field of regard with respect to the refueling device.33. The refueling device according to claim 32, wherein said imagingsystem is configured for providing at least one of 2D images,stereoscopic images, and 3D images of a sensing volume defined by saidfield of regard, and/or for providing said image data in real time. 34.The refueling device according to claim 31, wherein said imaging systemcomprises at least one LIDAR unit.
 35. The refueling device according toany one of claims 31 to 34, wherein said imaging system comprises or isoperatively connected to a computing system configured for identifying afuel receptacle of a receiver aircraft within said field of regard fromsaid image data, and for determining a spatial disposition of said fueldelivery nozzle with respect to the fuel receptacle.
 36. The refuelingdevice according to any one of claims 1 to 35, further comprising asuitable controller for controlling operation thereof.
 37. A refuelingdevice for use in in-flight refueling operation, comprising: (a) a bodyhaving a longitudinal axis and configured for being towed by a tankeraircraft via a fuel hose at least during in-flight refueling operation,and comprising a boom member having a boom axis and configured to enablefuel to be transferred from said fuel hose to a receiver aircraft alongsaid axis during said in-flight refueling operation; (b) said boommember being pivotable with respect to said body, between a retractedposition and a deployed position, wherein in said retracted positionsaid boom axis is at a smaller angular disposition with respect to saidlongitudinal axis than in said deployed position (c) spatial controlsystem including two sets of longitudinally spaced control surfacesconfigured for enabling selectively steering said refueling device whileconcurrently selectively maintaining a desired non-zero angulardisposition between said boom axis and said longitudinal axis at leastwhen said refueling device is towed by the tanker aircraft in saidforward direction via said fuel hose.
 38. A refueling device for use inin-flight refueling operation, comprising: (a) a body configured forbeing towed by a tanker aircraft via a fuel hose at least duringin-flight refueling operation, and comprising a boom member having aboom axis and configured to enable fuel to be transferred from said fuelhose to a receiver aircraft along said axis during said in-flightrefueling operation; (b) a force generating arrangement configured forselectively generating a force along said boom axis in a directiongenerally away from said fuel hose.
 39. A refueling device for use inin-flight refueling, comprising: (a) a body configured for being towedby a tanker aircraft via a fuel hose at least during in-flight refuelingoperation, and comprising a fuel delivery lumen configured for fluidcommunication with said fuel hose at least during the in-flightrefueling operation, said lumen being configured to enable fuel to betransferred from the fuel hose to a receiver aircraft during saidin-flight refueling operation; (b) a coupling having a hose interfaceconfigured for connecting said lumen to the fuel hose, said couplingconfigured for allowing relative rotation between the hose and said bodyin at least one degree of freedom while maintaining said fuelcommunication.
 40. A refueling system comprising a refueling fuelreservoir connected to a refueling device via a hose, the refuelingdevice being as defined in any one of claims 1 to
 39. 41. A tankeraircraft comprising at least one refueling system as defined in claim40.
 42. A refueling device for use in in-flight refueling operationbetween a tanker aircraft and a receiver aircraft, comprising: aselectively steerable body configured for being towed by a tankeraircraft via a fuel hose at least during in-flight refueling, andcomprising a boom member having a boom axis and configured to enablefuel to be transferred from said fuel hose to a receiver aircraft alongsaid boom axis during said in-flight refueling operation; a controllerconfigured for selectively steering the body to an engagement enablingposition spaced with respect to the receiver aircraft and for aligningsaid boom axis in an engagement enabling orientation at said spacedposition, and for subsequently moving the boom member along said boomaxis towards the receiver aircraft for enabling fuel communicationtherebetween.